<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:79121b2d-e854-41aa-aab3-7b5c5847e030,g:aa7e8fee-abd8-4fff-b3c4-f8ba25538e22-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.icumed.com/role/AuditInformation" xlink:type="simple" xlink:href="icui-20211231.xsd#AuditInformation"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AuditInformation" xlink:type="extended" id="i632e5b2db4164418a413a10710d0ece9_AuditInformation">
    <link:loc xlink:type="locator" xlink:label="loc_dei_AuditorLineItems_81a8c8fa-3747-4e21-bd78-7bea4c442447" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AuditorLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AuditorName_4b0fdbe3-360e-4d75-b76d-a89bf6b7613e" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AuditorName"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_AuditorLineItems_81a8c8fa-3747-4e21-bd78-7bea4c442447" xlink:to="loc_dei_AuditorName_4b0fdbe3-360e-4d75-b76d-a89bf6b7613e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AuditorLocation_510f5205-b47c-4c99-9b81-135cac9dd792" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AuditorLocation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_AuditorLineItems_81a8c8fa-3747-4e21-bd78-7bea4c442447" xlink:to="loc_dei_AuditorLocation_510f5205-b47c-4c99-9b81-135cac9dd792" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AuditorFirmId_56ade0b7-f3f9-4ad3-9aa8-1d12df4ff6f3" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AuditorFirmId"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_AuditorLineItems_81a8c8fa-3747-4e21-bd78-7bea4c442447" xlink:to="loc_dei_AuditorFirmId_56ade0b7-f3f9-4ad3-9aa8-1d12df4ff6f3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_AuditorTable_470b6a4c-0e56-497d-944d-85f18d275025" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_AuditorTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_dei_AuditorLineItems_81a8c8fa-3747-4e21-bd78-7bea4c442447" xlink:to="loc_dei_AuditorTable_470b6a4c-0e56-497d-944d-85f18d275025" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_LegalEntityAxis_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LegalEntityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_dei_AuditorTable_470b6a4c-0e56-497d-944d-85f18d275025" xlink:to="loc_dei_LegalEntityAxis_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6_default" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6" xlink:to="loc_dei_EntityDomain_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_dei_EntityDomain_f0afa126-6f6b-4ca9-a9cf-020711f649e7" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_7dee6a5c-fe5a-449c-aa27-a4c7e108d3a6" xlink:to="loc_dei_EntityDomain_f0afa126-6f6b-4ca9-a9cf-020711f649e7" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ConsolidatedBalanceSheets" xlink:type="simple" xlink:href="icui-20211231.xsd#ConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ConsolidatedBalanceSheets" xlink:type="extended" id="i782d876fd4e84d458c765acebd0d9073_ConsolidatedBalanceSheets">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_15267072-2051-4318-8eab-eaaa4b65ddd2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_15267072-2051-4318-8eab-eaaa4b65ddd2" xlink:to="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_e84c95fc-7ad0-4c29-a1f8-4965b697e73b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_e84c95fc-7ad0-4c29-a1f8-4965b697e73b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_1108b5c2-257e-4ad7-898f-03d8c2af5887" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_1108b5c2-257e-4ad7-898f-03d8c2af5887" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_0ffd47d9-a084-493b-89c2-9a418d7c5ae3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_0ffd47d9-a084-493b-89c2-9a418d7c5ae3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_f56c79c3-c9ab-461a-af6e-3f2a56cc44b4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_f56c79c3-c9ab-461a-af6e-3f2a56cc44b4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_67201777-b74f-4e52-b056-f86f669f6c90" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_InventoryNet_67201777-b74f-4e52-b056-f86f669f6c90" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidTaxes_77df12b3-ecd6-43ee-84c6-84512cab146a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_PrepaidTaxes_77df12b3-ecd6-43ee-84c6-84512cab146a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_889a4ae1-b6b5-4ba9-9ef2-8164ad76a0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_889a4ae1-b6b5-4ba9-9ef2-8164ad76a0c6" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_9636c861-29d7-4d00-ba07-5f70f3dd40dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_dfdce09e-b84a-45cb-94e8-a10f913ad8b4" xlink:to="loc_us-gaap_AssetsCurrent_9636c861-29d7-4d00-ba07-5f70f3dd40dd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_a8733971-c243-486f-9d50-f1cdc11f144f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_a8733971-c243-486f-9d50-f1cdc11f144f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_eaff121e-1d78-49af-9ac2-b0ba58d5eab0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_eaff121e-1d78-49af-9ac2-b0ba58d5eab0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_f9970f7d-7842-4af3-8bd3-2bddceba6d14" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_f9970f7d-7842-4af3-8bd3-2bddceba6d14" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_b03445a5-365b-4d21-83f5-894557e871b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_Goodwill_b03445a5-365b-4d21-83f5-894557e871b1" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_29701989-1728-4bbe-aedc-0856a4607bd0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_29701989-1728-4bbe-aedc-0856a4607bd0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_510d6626-30b3-4ce9-af52-5fe43b8cb414" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_510d6626-30b3-4ce9-af52-5fe43b8cb414" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_b86ce56a-a2cd-4586-bb19-53faf2b15cb7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_b86ce56a-a2cd-4586-bb19-53faf2b15cb7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_bf9f80e3-7fa5-41a2-9b7a-cc1457c1def3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_dedd0ab8-b22d-4e69-b6fb-068c36e6893f" xlink:to="loc_us-gaap_Assets_bf9f80e3-7fa5-41a2-9b7a-cc1457c1def3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_15267072-2051-4318-8eab-eaaa4b65ddd2" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_a4a5e46f-ea2a-4493-8db3-4ec6f2fde6e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:to="loc_us-gaap_AccountsPayableCurrent_a4a5e46f-ea2a-4493-8db3-4ec6f2fde6e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_de33b207-53b2-4a23-bf6e-83e4f060c7e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_de33b207-53b2-4a23-bf6e-83e4f060c7e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_3b5452f2-448a-4d1b-b9bd-f202ee09fd49" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_3b5452f2-448a-4d1b-b9bd-f202ee09fd49" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_366f0699-6e3c-42e2-a742-f36422a27d72" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_366f0699-6e3c-42e2-a742-f36422a27d72" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_37b8f6b0-6c04-4e6a-aae8-8a6118e5e02e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_2702a891-0e11-4370-9b5e-24cee3edb01e" xlink:to="loc_us-gaap_LiabilitiesCurrent_37b8f6b0-6c04-4e6a-aae8-8a6118e5e02e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_ed369667-9db0-4b58-b35d-1379a0201ba4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_ed369667-9db0-4b58-b35d-1379a0201ba4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities_ac3e98a8-a51a-46a2-b8e0-56bea59f5f4e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_OtherLiabilities_ac3e98a8-a51a-46a2-b8e0-56bea59f5f4e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_e47d39a4-789e-4389-bc2c-e51d6d3b56f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_e47d39a4-789e-4389-bc2c-e51d6d3b56f7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_5b1ad894-0242-410a-9038-82c6d8bdf690" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedIncomeTaxesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_5b1ad894-0242-410a-9038-82c6d8bdf690" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_92eaba50-a570-4c5d-a236-645ed88a7e70" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_CommitmentsAndContingencies_92eaba50-a570-4c5d-a236-645ed88a7e70" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_a2ecd64a-7451-416d-ad0c-a0745e458e80" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_a2ecd64a-7451-416d-ad0c-a0745e458e80" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_3c90e86a-d931-4c79-967c-794243445186" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_CommonStockValue_3c90e86a-d931-4c79-967c-794243445186" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_1966b99a-c569-42b1-89f8-fd5f015089c4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_1966b99a-c569-42b1-89f8-fd5f015089c4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_79ea34e6-ed9f-4fac-afea-2d93f4765e5e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_TreasuryStockValue_79ea34e6-ed9f-4fac-afea-2d93f4765e5e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3d0c3a30-fa3e-4007-b3ec-e802f7aa5a3d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_3d0c3a30-fa3e-4007-b3ec-e802f7aa5a3d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_3db2ae83-3655-4ac4-925e-55153fdd3182" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_3db2ae83-3655-4ac4-925e-55153fdd3182" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_4f8f4883-308c-414d-b95d-8ac92fc1c786" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_aa019921-0952-4c17-bfe7-85dba7ea4b3b" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_4f8f4883-308c-414d-b95d-8ac92fc1c786" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_063264ba-8a9e-4098-bd3c-ae018987c338" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_a597816f-4a22-41ea-a7ba-45a2b8286807" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_063264ba-8a9e-4098-bd3c-ae018987c338" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_815ba3f3-a9f2-4dc9-a758-c534636204a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_15267072-2051-4318-8eab-eaaa4b65ddd2" xlink:to="loc_us-gaap_StatementTable_815ba3f3-a9f2-4dc9-a758-c534636204a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_481d5305-d5f7-477d-bb68-baba7be3f41c" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_815ba3f3-a9f2-4dc9-a758-c534636204a0" xlink:to="loc_srt_StatementScenarioAxis_481d5305-d5f7-477d-bb68-baba7be3f41c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_481d5305-d5f7-477d-bb68-baba7be3f41c_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_481d5305-d5f7-477d-bb68-baba7be3f41c" xlink:to="loc_srt_ScenarioUnspecifiedDomain_481d5305-d5f7-477d-bb68-baba7be3f41c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_52c6160d-f1a3-4a77-821c-a9fde3482144" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_481d5305-d5f7-477d-bb68-baba7be3f41c" xlink:to="loc_srt_ScenarioUnspecifiedDomain_52c6160d-f1a3-4a77-821c-a9fde3482144" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="icui-20211231.xsd#ConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ConsolidatedStatementsofIncome" xlink:type="extended" id="i91447087852b4863969636485a432a4e_ConsolidatedStatementsofIncome">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_35d7a73e-c5cc-4e6f-bad5-fefd35f06ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_RevenuesAbstract_35d7a73e-c5cc-4e6f-bad5-fefd35f06ef1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_0cdb274b-be8c-48c3-b7fa-8c3a9b018638" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_35d7a73e-c5cc-4e6f-bad5-fefd35f06ef1" xlink:to="loc_us-gaap_Revenues_0cdb274b-be8c-48c3-b7fa-8c3a9b018638" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfGoodsAndServicesSold_4583ce40-b9df-4fdb-8356-2f3794ff8796" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfGoodsAndServicesSold"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_CostOfGoodsAndServicesSold_4583ce40-b9df-4fdb-8356-2f3794ff8796" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_a9137ded-e180-45c3-8581-5fb6cb60ee9a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_GrossProfit_a9137ded-e180-45c3-8581-5fb6cb60ee9a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_8dd99195-2f38-4fe6-8300-174516682659" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_8dd99195-2f38-4fe6-8300-174516682659" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_822428bc-0b39-4355-8eb5-bfb17175960d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_822428bc-0b39-4355-8eb5-bfb17175960d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Restructuringandstrategictransactionexpense_c67f2b6e-0bba-488d-82e0-9946594cd7ee" xlink:href="icui-20211231.xsd#icui_Restructuringandstrategictransactionexpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_icui_Restructuringandstrategictransactionexpense_c67f2b6e-0bba-488d-82e0-9946594cd7ee" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_fca80432-afcb-42a0-85d4-411fdbb0cdfe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_fca80432-afcb-42a0-85d4-411fdbb0cdfe" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contractsettlements_aa9b22ff-b2f1-4c04-ac01-294ca582e5f8" xlink:href="icui-20211231.xsd#icui_Contractsettlements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_icui_Contractsettlements_aa9b22ff-b2f1-4c04-ac01-294ca582e5f8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_6cdd707c-cf28-4cab-99c0-1aaeaea0d66a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_fe01fc27-0c06-48bc-a937-85a805f0e221" xlink:to="loc_us-gaap_OperatingExpenses_6cdd707c-cf28-4cab-99c0-1aaeaea0d66a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_59d6e0ac-4d73-467f-8b68-5fb54028d1e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_OperatingIncomeLoss_59d6e0ac-4d73-467f-8b68-5fb54028d1e1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_4fb2a991-b917-4405-93c9-bbcbbb3b0be4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_InterestExpense_4fb2a991-b917-4405-93c9-bbcbbb3b0be4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_b6229e52-c4f3-40ed-bca0-7e4bc7ef0dc2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_b6229e52-c4f3-40ed-bca0-7e4bc7ef0dc2" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossAttributableToParent_0b73c418-a252-473b-ad87-c144637f7938" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_IncomeLossAttributableToParent_0b73c418-a252-473b-ad87-c144637f7938" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_9ffd0ca5-0df9-44bd-90ca-b57d507ec433" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_9ffd0ca5-0df9-44bd-90ca-b57d507ec433" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_6d033949-2f91-42d2-88d0-0fd765f5205c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_NetIncomeLoss_6d033949-2f91-42d2-88d0-0fd765f5205c" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_d88b9ca7-1252-4f1d-90cb-75f05c863877" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_EarningsPerShareBasic_d88b9ca7-1252-4f1d-90cb-75f05c863877" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_312c682e-c532-42b3-a9d5-d0099feb2127" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_EarningsPerShareDiluted_312c682e-c532-42b3-a9d5-d0099feb2127" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ce2d1e10-5a04-4981-a057-f9ede068f28f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ce2d1e10-5a04-4981-a057-f9ede068f28f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_f7766a8a-9de6-4212-b04a-4cda3e8240db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ce2d1e10-5a04-4981-a057-f9ede068f28f" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_f7766a8a-9de6-4212-b04a-4cda3e8240db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_852ca4b6-e342-4d6c-86a7-43129639136c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_ce2d1e10-5a04-4981-a057-f9ede068f28f" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_852ca4b6-e342-4d6c-86a7-43129639136c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_ca6c9532-38ca-45fa-8032-32ec45bdb0b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_55711c27-926d-44ba-b79c-97a835974afe" xlink:to="loc_us-gaap_StatementTable_ca6c9532-38ca-45fa-8032-32ec45bdb0b1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_9ce8dd5e-82ec-4104-8973-a7afa8944a01" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_ca6c9532-38ca-45fa-8032-32ec45bdb0b1" xlink:to="loc_srt_ProductOrServiceAxis_9ce8dd5e-82ec-4104-8973-a7afa8944a01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_9ce8dd5e-82ec-4104-8973-a7afa8944a01_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_9ce8dd5e-82ec-4104-8973-a7afa8944a01" xlink:to="loc_srt_ProductsAndServicesDomain_9ce8dd5e-82ec-4104-8973-a7afa8944a01_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_b34cf841-81ac-4565-ae1e-3594d074b45b" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_9ce8dd5e-82ec-4104-8973-a7afa8944a01" xlink:to="loc_srt_ProductsAndServicesDomain_b34cf841-81ac-4565-ae1e-3594d074b45b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/StatementofComprehensiveIncome" xlink:type="simple" xlink:href="icui-20211231.xsd#StatementofComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/StatementofComprehensiveIncome" xlink:type="extended" id="id3aae23f55a04ab0bb62aa323989c12e_StatementofComprehensiveIncome">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_c12087b1-799a-4a09-b0de-e9385ea158ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_NetIncomeLoss_c12087b1-799a-4a09-b0de-e9385ea158ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_abd44712-13fb-4f98-9cfd-e943fd8fe923" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_abd44712-13fb-4f98-9cfd-e943fd8fe923" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_d3e09bf7-e140-4da7-87a0-ae702b8bf84f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationAdjustmentNetOfTaxPortionAttributableToParent_d3e09bf7-e140-4da7-87a0-ae702b8bf84f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_54b044e4-3f01-4c91-852a-4bf7f85bb050" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_54b044e4-3f01-4c91-852a-4bf7f85bb050" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_373e8922-40eb-4bcd-8347-46a742e61852" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_373e8922-40eb-4bcd-8347-46a742e61852" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_653521ef-edac-4867-864e-694fbc41c9d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_653521ef-edac-4867-864e-694fbc41c9d5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_d48127e5-0280-4b0f-b5d7-4838b739b40f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_2ac19b1d-966b-46d0-8aac-d42fc634eeb2" xlink:to="loc_us-gaap_StatementTable_d48127e5-0280-4b0f-b5d7-4838b739b40f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_3b531d8e-4cf5-4069-8975-1b9725f1f1ac" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_d48127e5-0280-4b0f-b5d7-4838b739b40f" xlink:to="loc_srt_StatementScenarioAxis_3b531d8e-4cf5-4069-8975-1b9725f1f1ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_3b531d8e-4cf5-4069-8975-1b9725f1f1ac_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_3b531d8e-4cf5-4069-8975-1b9725f1f1ac" xlink:to="loc_srt_ScenarioUnspecifiedDomain_3b531d8e-4cf5-4069-8975-1b9725f1f1ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_29f20c6a-0f88-465f-a9fe-60c6351aca79" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_3b531d8e-4cf5-4069-8975-1b9725f1f1ac" xlink:to="loc_srt_ScenarioUnspecifiedDomain_29f20c6a-0f88-465f-a9fe-60c6351aca79" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="simple" xlink:href="icui-20211231.xsd#ConsolidatedStatementsofStockholdersEquity"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ConsolidatedStatementsofStockholdersEquity" xlink:type="extended" id="i84e17e241f6945359eae0843370d9ae7_ConsolidatedStatementsofStockholdersEquity">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_6bbe099a-2065-460d-832c-ef43d21af34b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6bbe099a-2065-460d-832c-ef43d21af34b" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_d2be5d13-e8ec-4368-80ea-b1261210618d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_d2be5d13-e8ec-4368-80ea-b1261210618d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_0709cba2-5e8c-4ef1-9ae3-d46e2fc3a635" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_StockholdersEquity_0709cba2-5e8c-4ef1-9ae3-d46e2fc3a635" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_6846bd8f-6dd7-48ad-8cb0-e088bd236ae9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_6846bd8f-6dd7-48ad-8cb0-e088bd236ae9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6500c7cf-da06-47e0-b7dc-a69074a5a174" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_6500c7cf-da06-47e0-b7dc-a69074a5a174" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_9229ed96-f993-484a-a90c-e537863ed7a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockSharesAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_9229ed96-f993-484a-a90c-e537863ed7a8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_05486dfb-bf47-4d23-acb1-bf8aae89413c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_05486dfb-bf47-4d23-acb1-bf8aae89413c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_65bb2f85-6083-4c33-9a21-c26748a9ce0e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_65bb2f85-6083-4c33-9a21-c26748a9ce0e" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_890056cf-5474-4e13-afb4-da7f19b51d20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_890056cf-5474-4e13-afb4-da7f19b51d20" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_b19cdaf2-8076-418b-bca2-776df9c728df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_bd4d87d2-3a99-4eaf-97d0-f309b7adbd2f" xlink:to="loc_us-gaap_NetIncomeLoss_b19cdaf2-8076-418b-bca2-776df9c728df" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_cf1c2a9d-4c9b-4277-849b-e61eced54fec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_a1a9f8c0-a9c5-41f7-9540-042b1c748391" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_9cedd24a-765c-4e9f-b775-e824cd0f3182" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6bbe099a-2065-460d-832c-ef43d21af34b" xlink:to="loc_us-gaap_StatementTable_9cedd24a-765c-4e9f-b775-e824cd0f3182" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9259a533-0559-484b-8b0a-d08bad3ecfe4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9cedd24a-765c-4e9f-b775-e824cd0f3182" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9259a533-0559-484b-8b0a-d08bad3ecfe4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9259a533-0559-484b-8b0a-d08bad3ecfe4_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9259a533-0559-484b-8b0a-d08bad3ecfe4" xlink:to="loc_us-gaap_EquityComponentDomain_9259a533-0559-484b-8b0a-d08bad3ecfe4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9259a533-0559-484b-8b0a-d08bad3ecfe4" xlink:to="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CommonStockSharesMember_cd910e7b-15d3-44a3-84b1-7981bf8c7920" xlink:href="icui-20211231.xsd#icui_CommonStockSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_icui_CommonStockSharesMember_cd910e7b-15d3-44a3-84b1-7981bf8c7920" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_2997ece3-dbfa-4156-b2b7-c928c2e18a72" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_us-gaap_CommonStockMember_2997ece3-dbfa-4156-b2b7-c928c2e18a72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_c0c6501f-a40d-4414-8c05-76a5b0924b65" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_c0c6501f-a40d-4414-8c05-76a5b0924b65" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_c334cefc-9446-4c45-becf-5a9fa1e533b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_us-gaap_TreasuryStockMember_c334cefc-9446-4c45-becf-5a9fa1e533b6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_1587ca18-3e41-493b-836e-2535b399c4d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_us-gaap_RetainedEarningsMember_1587ca18-3e41-493b-836e-2535b399c4d6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_37937f71-8773-4b6d-abb2-b8bf152eac02" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_c7f1cd4a-83e6-45bd-a8e2-7fb7391246d4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_37937f71-8773-4b6d-abb2-b8bf152eac02" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="icui-20211231.xsd#ConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ConsolidatedStatementsofCashFlows" xlink:type="extended" id="ie8397325b4264f0199a3b535bccb1023_ConsolidatedStatementsofCashFlows">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_d622effa-673e-481a-9b92-ebe88d6042e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_d622effa-673e-481a-9b92-ebe88d6042e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_d622effa-673e-481a-9b92-ebe88d6042e7" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_850f8e3a-c3ce-4fd8-8b48-c0e1479b8a2b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_NetIncomeLoss_850f8e3a-c3ce-4fd8-8b48-c0e1479b8a2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_8661c320-e60f-41da-bf35-fcb7baa08ea7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_8661c320-e60f-41da-bf35-fcb7baa08ea7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Operatingleaserightofuseassetamortization_c1ae0339-5f0c-4b9f-8f09-d66ba1bc9f9a" xlink:href="icui-20211231.xsd#icui_Operatingleaserightofuseassetamortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_icui_Operatingleaserightofuseassetamortization_c1ae0339-5f0c-4b9f-8f09-d66ba1bc9f9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_e6cd1e6b-f7ea-4fcf-9c39-d9a5e11ab4e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_e6cd1e6b-f7ea-4fcf-9c39-d9a5e11ab4e0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ProvisionForWarrantyAndReturns_5138c3c3-d9d6-4db4-8ee3-7da91baf6f5f" xlink:href="icui-20211231.xsd#icui_ProvisionForWarrantyAndReturns"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_icui_ProvisionForWarrantyAndReturns_5138c3c3-d9d6-4db4-8ee3-7da91baf6f5f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_ae1472b1-096a-4138-83ed-6cd6a4776a5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_ShareBasedCompensation_ae1472b1-096a-4138-83ed-6cd6a4776a5a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_bdd8f302-b0f1-4c38-ade9-872189784f6c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_bdd8f302-b0f1-4c38-ade9-872189784f6c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_e2eab5dd-8d87-49ab-a683-0fbaa3576c49" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InvestmentIncomeAmortizationOfPremium"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_e2eab5dd-8d87-49ab-a683-0fbaa3576c49" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_f6b50eab-060c-46c2-b162-7d90ab68ede3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_f6b50eab-060c-46c2-b162-7d90ab68ede3" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_b398f845-9bbd-45b7-9705-d05ee1d8b61f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_b398f845-9bbd-45b7-9705-d05ee1d8b61f" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductionRelatedImpairmentsOrCharges_4144d2b8-f83e-4cf1-b0fe-89726460f2d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductionRelatedImpairmentsOrCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_ProductionRelatedImpairmentsOrCharges_4144d2b8-f83e-4cf1-b0fe-89726460f2d8" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Sparepartsusage_7d3df8c5-3d99-409b-b68e-e4df3232eacb" xlink:href="icui-20211231.xsd#icui_Sparepartsusage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_icui_Sparepartsusage_7d3df8c5-3d99-409b-b68e-e4df3232eacb" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_a324b292-9f19-4da6-a0c8-d89f7c00c612" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherOperatingActivitiesCashFlowStatement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_OtherOperatingActivitiesCashFlowStatement_a324b292-9f19-4da6-a0c8-d89f7c00c612" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_5c89e122-735c-4c4e-bdc9-6c5be58cfe60" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_5c89e122-735c-4c4e-bdc9-6c5be58cfe60" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_55b4535d-ab77-45c4-a4f6-719e48333e7e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_55b4535d-ab77-45c4-a4f6-719e48333e7e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_1e6ad5d1-138c-4406-9236-f2c298119c21" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_1e6ad5d1-138c-4406-9236-f2c298119c21" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_e389c631-0853-49f0-98cb-3019d9511a87" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_e389c631-0853-49f0-98cb-3019d9511a87" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_bc173d4c-cdf6-4929-9119-c1c7bb0b91bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_bc173d4c-cdf6-4929-9119-c1c7bb0b91bf" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_d83a92e8-8c28-463c-b749-b8282d847570" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_d83a92e8-8c28-463c-b749-b8282d847570" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_8b6370af-b81f-42cf-961a-23dfc4ab1db5" xlink:href="icui-20211231.xsd#icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_bad8afe9-a957-4c6e-a2ce-6e38b3688aa0" xlink:to="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_8b6370af-b81f-42cf-961a-23dfc4ab1db5" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_85ea4da9-a94d-48a0-bc36-f392b461312f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_85ea4da9-a94d-48a0-bc36-f392b461312f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_e45805ea-5040-466b-937a-17f2a3de8bf0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_e45805ea-5040-466b-937a-17f2a3de8bf0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfOtherPropertyPlantAndEquipment_527127d6-eb7a-4bde-9cf8-4e059c3bb8f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromSaleOfOtherPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_ProceedsFromSaleOfOtherPropertyPlantAndEquipment_527127d6-eb7a-4bde-9cf8-4e059c3bb8f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_791a1d06-e3f4-46aa-896f-8c98498b907e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_791a1d06-e3f4-46aa-896f-8c98498b907e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bc8399d4-f228-40a6-b2a3-c9c8bc35e358" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bc8399d4-f228-40a6-b2a3-c9c8bc35e358" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_475b7e67-e4f6-4155-8714-2408e7c295bd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireEquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_PaymentsToAcquireEquityMethodInvestments_475b7e67-e4f6-4155-8714-2408e7c295bd" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireMarketableSecurities_4b10d4f3-d8ff-4cda-96a0-3a464bdfc896" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_PaymentsToAcquireMarketableSecurities_4b10d4f3-d8ff-4cda-96a0-3a464bdfc896" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_dc80af41-a849-48f8-ba05-fbb56c201c79" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_92770442-25b5-4b7f-b14d-b3bb37aff145" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_dc80af41-a849-48f8-ba05-fbb56c201c79" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_281d6680-6751-485e-9fd1-bbb84ac29c5f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_281d6680-6751-485e-9fd1-bbb84ac29c5f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_35f4a0bd-de63-4251-89f9-6df85d6f3525" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromLongTermLinesOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_ProceedsFromLongTermLinesOfCredit_35f4a0bd-de63-4251-89f9-6df85d6f3525" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_a383271a-4751-4748-b51b-45a8ff6df43a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_a383271a-4751-4748-b51b-45a8ff6df43a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_d33c6ca2-daf7-4cce-bd33-fd7f1a13d980" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_d33c6ca2-daf7-4cce-bd33-fd7f1a13d980" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_def8ba45-c1d0-4ddc-8bfd-7cdcc4382a45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_def8ba45-c1d0-4ddc-8bfd-7cdcc4382a45" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_855b0442-618d-482b-ad34-61e7a881dce2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_855b0442-618d-482b-ad34-61e7a881dce2" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_733129f6-336c-49b7-9806-37d061048979" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_1b780457-97af-449b-bd63-4ccd0810eb5a" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_733129f6-336c-49b7-9806-37d061048979" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_721a7a2a-1ec0-40b0-8c3e-561e37787e29" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_97a10eec-0aa2-4275-979e-42d6d81b797e" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_721a7a2a-1ec0-40b0-8c3e-561e37787e29" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_91c38c3c-6630-44c2-a838-0fcd64b252b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_d622effa-673e-481a-9b92-ebe88d6042e7" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_91c38c3c-6630-44c2-a838-0fcd64b252b3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_6be183bd-1212-4082-ae0e-7572961ee2dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_91c38c3c-6630-44c2-a838-0fcd64b252b3" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_6be183bd-1212-4082-ae0e-7572961ee2dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_0a26fcf4-5a91-4987-9d23-7325e5fef86e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_91c38c3c-6630-44c2-a838-0fcd64b252b3" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_0a26fcf4-5a91-4987-9d23-7325e5fef86e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_0e59aa67-0796-4e1f-b7e5-07647e7acbfd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_0e59aa67-0796-4e1f-b7e5-07647e7acbfd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_83909daa-9cca-4d30-9702-4a6bb44166e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_88687425-be68-470a-aac2-2af8c349529c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_88687425-be68-470a-aac2-2af8c349529c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxesPaid_a7de8e8b-1b29-4e01-b153-48662d66204d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxesPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_88687425-be68-470a-aac2-2af8c349529c" xlink:to="loc_us-gaap_IncomeTaxesPaid_a7de8e8b-1b29-4e01-b153-48662d66204d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestPaidNet_32710778-4608-4434-ac3f-0469c2cbb2fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestPaidNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_88687425-be68-470a-aac2-2af8c349529c" xlink:to="loc_us-gaap_InterestPaidNet_32710778-4608-4434-ac3f-0469c2cbb2fa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_ebf204fa-5759-4608-8d61-bece94408564" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_ebf204fa-5759-4608-8d61-bece94408564" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOfAssetsAcquired_b7ecd8f5-32be-4f96-a3fc-14cde1641365" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueOfAssetsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_FairValueOfAssetsAcquired_b7ecd8f5-32be-4f96-a3fc-14cde1641365" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NetCashPaidReceivedforcurrentandprioracquisitions_c497f8a0-9900-4c4e-9f16-a3b45d823996" xlink:href="icui-20211231.xsd#icui_NetCashPaidReceivedforcurrentandprioracquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_icui_NetCashPaidReceivedforcurrentandprioracquisitions_c497f8a0-9900-4c4e-9f16-a3b45d823996" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationLiabilitiesArisingFromContingenciesAmountRecognized_bd34d331-6628-4268-8e11-543c79ca8a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationLiabilitiesArisingFromContingenciesAmountRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_BusinessCombinationLiabilitiesArisingFromContingenciesAmountRecognized_bd34d331-6628-4268-8e11-543c79ca8a4d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPeriodIncreaseDecrease_d90773af-5522-4a08-b59c-b3ba76f0c7da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillPeriodIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_GoodwillPeriodIncreaseDecrease_d90773af-5522-4a08-b59c-b3ba76f0c7da" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_3f5cbd41-4a70-4200-948d-e20ea9b0b520" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_3f5cbd41-4a70-4200-948d-e20ea9b0b520" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAssumed1_107fa45a-ec43-4971-843d-6dc5b7e3b03a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAssumed1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_f7d20094-45b9-4598-9d40-8641e0dd0282" xlink:to="loc_us-gaap_LiabilitiesAssumed1_107fa45a-ec43-4971-843d-6dc5b7e3b03a" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_34531e7b-49e5-43dc-9caa-ab46b2b01ebb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_5a888d6a-08d1-49fa-852c-3cb69e935ec0" xlink:to="loc_us-gaap_StatementTable_34531e7b-49e5-43dc-9caa-ab46b2b01ebb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_d99dd388-9c4b-4041-a528-79fb55852c03" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_34531e7b-49e5-43dc-9caa-ab46b2b01ebb" xlink:to="loc_srt_StatementScenarioAxis_d99dd388-9c4b-4041-a528-79fb55852c03" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_d99dd388-9c4b-4041-a528-79fb55852c03_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_d99dd388-9c4b-4041-a528-79fb55852c03" xlink:to="loc_srt_ScenarioUnspecifiedDomain_d99dd388-9c4b-4041-a528-79fb55852c03_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_d7cff203-558c-466f-adcb-f5522dc6c4d6" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_d99dd388-9c4b-4041-a528-79fb55852c03" xlink:to="loc_srt_ScenarioUnspecifiedDomain_d7cff203-558c-466f-adcb-f5522dc6c4d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_63511aa3-6c0e-42b1-8a93-e73963d8f361" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_34531e7b-49e5-43dc-9caa-ab46b2b01ebb" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_63511aa3-6c0e-42b1-8a93-e73963d8f361" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_63511aa3-6c0e-42b1-8a93-e73963d8f361_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_63511aa3-6c0e-42b1-8a93-e73963d8f361" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_63511aa3-6c0e-42b1-8a93-e73963d8f361_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_63511aa3-6c0e-42b1-8a93-e73963d8f361" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalDistributorMember_ce5a28a1-d61d-4d11-a104-ddefb872ca35" xlink:href="icui-20211231.xsd#icui_InternationalDistributorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:to="loc_icui_InternationalDistributorMember_ce5a28a1-d61d-4d11-a104-ddefb872ca35" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_dc613888-31cc-4624-b477-4f69ccc1e3ef" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:to="loc_icui_PursuitVascularLLCMember_dc613888-31cc-4624-b477-4f69ccc1e3ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_c4e48f7c-78e2-4c02-88f3-da707157cc4b" xlink:href="icui-20211231.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_c4e48f7c-78e2-4c02-88f3-da707157cc4b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TotalAcquisitionsMember_54ab4fbb-c472-4df7-8eaf-1317f06d70fa" xlink:href="icui-20211231.xsd#icui_TotalAcquisitionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c081f08d-4b40-4bf1-819a-92269f800b81" xlink:to="loc_icui_TotalAcquisitionsMember_54ab4fbb-c472-4df7-8eaf-1317f06d70fa" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment1Details" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment1Details"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment1Details" xlink:type="extended" id="ie76b64e716314aa598504ac5bba637ed_GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment1Details">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_98909775-eb34-4264-8430-04bbb1148bd5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_7726981d-46fd-4443-bde1-219a5cace5da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_98909775-eb34-4264-8430-04bbb1148bd5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_7726981d-46fd-4443-bde1-219a5cace5da" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_3f4cf066-34df-4d78-bc20-4fd55d3f1656" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_98909775-eb34-4264-8430-04bbb1148bd5" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_3f4cf066-34df-4d78-bc20-4fd55d3f1656" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_edde4be2-7094-453e-97d7-c741f0997634" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_98909775-eb34-4264-8430-04bbb1148bd5" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_edde4be2-7094-453e-97d7-c741f0997634" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_eb630ccb-2338-4872-8001-7dc355c36e88" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_98909775-eb34-4264-8430-04bbb1148bd5" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_eb630ccb-2338-4872-8001-7dc355c36e88" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_371c564c-53d9-4e58-8972-2f8133bb0879" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_eb630ccb-2338-4872-8001-7dc355c36e88" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_371c564c-53d9-4e58-8972-2f8133bb0879" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_371c564c-53d9-4e58-8972-2f8133bb0879_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_371c564c-53d9-4e58-8972-2f8133bb0879" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_371c564c-53d9-4e58-8972-2f8133bb0879_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_371c564c-53d9-4e58-8972-2f8133bb0879" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_e30f9182-5d6c-47eb-abfd-c6ba2df6a58a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_e30f9182-5d6c-47eb-abfd-c6ba2df6a58a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_52a8d358-5ac8-45ac-964f-8b4ee0222964" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LandBuildingsAndImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_52a8d358-5ac8-45ac-964f-8b4ee0222964" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MoldsMember_3e54a1e3-6fe3-43a4-89ed-e624917289ca" xlink:href="icui-20211231.xsd#icui_MoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_icui_MoldsMember_3e54a1e3-6fe3-43a4-89ed-e624917289ca" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ComputerEquipmentAndSoftwareMember_46285db6-7d4f-4443-a0a3-90c206278e7a" xlink:href="icui-20211231.xsd#icui_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_icui_ComputerEquipmentAndSoftwareMember_46285db6-7d4f-4443-a0a3-90c206278e7a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesMember_c3c8f2a9-012d-491a-99cf-50565d9664d5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_us-gaap_FurnitureAndFixturesMember_c3c8f2a9-012d-491a-99cf-50565d9664d5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InstrumentsPlacedwithCustomersMember_4de3f08d-91e9-4aa5-8e1b-9002f96d2268" xlink:href="icui-20211231.xsd#icui_InstrumentsPlacedwithCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_icui_InstrumentsPlacedwithCustomersMember_4de3f08d-91e9-4aa5-8e1b-9002f96d2268" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressMember_1462c414-94f8-4da1-81d4-288dcefaa9d2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConstructionInProgressMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_6984fa2b-0f31-47ae-a0a5-bde769b77bae" xlink:to="loc_us-gaap_ConstructionInProgressMember_1462c414-94f8-4da1-81d4-288dcefaa9d2" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment2Details" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment2Details"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment2Details" xlink:type="extended" id="i5de79b40b8524f868ff708ab9bb54c5d_GeneralandSummaryofSignificantAccountingPoliciesPropertyandEquipment2Details">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a8664a63-182e-482e-bec8-0abd8cf9502a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives_4e767a81-cc21-4fc5-aa96-fb47f1735314" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a8664a63-182e-482e-bec8-0abd8cf9502a" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentEstimatedUsefulLives_4e767a81-cc21-4fc5-aa96-fb47f1735314" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_42bbd676-97af-4d80-9063-d10d99d9bf2b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_a8664a63-182e-482e-bec8-0abd8cf9502a" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_42bbd676-97af-4d80-9063-d10d99d9bf2b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0ec526f2-69e0-43bc-8306-ac5a5186def8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_42bbd676-97af-4d80-9063-d10d99d9bf2b" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0ec526f2-69e0-43bc-8306-ac5a5186def8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0ec526f2-69e0-43bc-8306-ac5a5186def8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0ec526f2-69e0-43bc-8306-ac5a5186def8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_0ec526f2-69e0-43bc-8306-ac5a5186def8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_0ec526f2-69e0-43bc-8306-ac5a5186def8" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingMember_f01c98d9-e179-457b-8189-c63f2f5ff82e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BuildingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_us-gaap_BuildingMember_f01c98d9-e179-457b-8189-c63f2f5ff82e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BuildingImprovementsMember_1a7561e1-c089-45ce-bb8c-981c67c4b79e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BuildingImprovementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_us-gaap_BuildingImprovementsMember_1a7561e1-c089-45ce-bb8c-981c67c4b79e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentMember_78a6781a-c46e-4139-b189-f2924eff97a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MachineryAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_us-gaap_MachineryAndEquipmentMember_78a6781a-c46e-4139-b189-f2924eff97a3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_FurniturefixturesandmoldsMember_c2f0e811-b9c1-411a-86ec-a14fb2557fe2" xlink:href="icui-20211231.xsd#icui_FurniturefixturesandmoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_icui_FurniturefixturesandmoldsMember_c2f0e811-b9c1-411a-86ec-a14fb2557fe2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ComputerEquipmentAndSoftwareMember_952e002c-2eeb-427a-8d95-5a9b9f12f786" xlink:href="icui-20211231.xsd#icui_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_icui_ComputerEquipmentAndSoftwareMember_952e002c-2eeb-427a-8d95-5a9b9f12f786" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InstrumentsPlacedwithCustomersMember_5ed0099e-27bc-4f41-b4fe-123917e239c9" xlink:href="icui-20211231.xsd#icui_InstrumentsPlacedwithCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_46222615-b6a1-4257-b1fe-3468b58476d9" xlink:to="loc_icui_InstrumentsPlacedwithCustomersMember_5ed0099e-27bc-4f41-b4fe-123917e239c9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_6990349d-c357-4c40-81f7-abd0352cfc3c" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_42bbd676-97af-4d80-9063-d10d99d9bf2b" xlink:to="loc_srt_RangeAxis_6990349d-c357-4c40-81f7-abd0352cfc3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_6990349d-c357-4c40-81f7-abd0352cfc3c_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_6990349d-c357-4c40-81f7-abd0352cfc3c" xlink:to="loc_srt_RangeMember_6990349d-c357-4c40-81f7-abd0352cfc3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9c89afc0-afbe-4e51-80cb-ebb6b70ded7c" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_6990349d-c357-4c40-81f7-abd0352cfc3c" xlink:to="loc_srt_RangeMember_9c89afc0-afbe-4e51-80cb-ebb6b70ded7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_304281aa-f9a2-4ca7-873f-69f3758068ed" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9c89afc0-afbe-4e51-80cb-ebb6b70ded7c" xlink:to="loc_srt_MinimumMember_304281aa-f9a2-4ca7-873f-69f3758068ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_cd778607-b373-4a5b-815b-81e4aa7f5b2e" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_9c89afc0-afbe-4e51-80cb-ebb6b70ded7c" xlink:to="loc_srt_MaximumMember_cd778607-b373-4a5b-815b-81e4aa7f5b2e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesGoodwillDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesGoodwillDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesGoodwillDetails" xlink:type="extended" id="icf8af3dc1a15476b82db20053592ec76_GeneralandSummaryofSignificantAccountingPoliciesGoodwillDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_ba4490b6-a338-4e71-9cef-f9e5b619b209" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_ba4490b6-a338-4e71-9cef-f9e5b619b209" xlink:to="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_97cd1a43-4ba6-45c3-89ac-013f6908f1fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:to="loc_us-gaap_Goodwill_97cd1a43-4ba6-45c3-89ac-013f6908f1fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_3a918e86-848e-4394-8997-d215d9b46665" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_3a918e86-848e-4394-8997-d215d9b46665" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_ea8a43b4-8cee-4de5-993d-a30a17148f90" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_ea8a43b4-8cee-4de5-993d-a30a17148f90" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_b80b016a-cb29-44ab-83fa-619d10c78c58" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_5ff6743f-b1b1-414b-b77f-d2c212b4f661" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_b80b016a-cb29-44ab-83fa-619d10c78c58" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_a7b07b22-2c73-4273-83e2-20930020e68a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Goodwill"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_3afd44fe-3564-4adc-9073-128ac93f8610" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_ba4490b6-a338-4e71-9cef-f9e5b619b209" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_3afd44fe-3564-4adc-9073-128ac93f8610" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_16d243bf-f97a-4a49-81e7-d59ad6614415" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_3afd44fe-3564-4adc-9073-128ac93f8610" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_16d243bf-f97a-4a49-81e7-d59ad6614415" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16d243bf-f97a-4a49-81e7-d59ad6614415_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_16d243bf-f97a-4a49-81e7-d59ad6614415" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16d243bf-f97a-4a49-81e7-d59ad6614415_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16e029aa-5feb-4ad7-9b15-a378feeb91f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_16d243bf-f97a-4a49-81e7-d59ad6614415" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16e029aa-5feb-4ad7-9b15-a378feeb91f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_2bfa2c7d-4474-4d0f-a931-07632bcce6db" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16e029aa-5feb-4ad7-9b15-a378feeb91f9" xlink:to="loc_icui_PursuitVascularLLCMember_2bfa2c7d-4474-4d0f-a931-07632bcce6db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignDistibutorMember_45871777-8663-452b-a1ec-7e42c7192dd3" xlink:href="icui-20211231.xsd#icui_ForeignDistibutorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16e029aa-5feb-4ad7-9b15-a378feeb91f9" xlink:to="loc_icui_ForeignDistibutorMember_45871777-8663-452b-a1ec-7e42c7192dd3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_367cb985-f3c0-4aaa-aa19-ad4cfec5526c" xlink:href="icui-20211231.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_16e029aa-5feb-4ad7-9b15-a378feeb91f9" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_367cb985-f3c0-4aaa-aa19-ad4cfec5526c" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesIntangibleAssets1Details" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesIntangibleAssets1Details"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesIntangibleAssets1Details" xlink:type="extended" id="if46543f751624374a178f677dba2a022_GeneralandSummaryofSignificantAccountingPoliciesIntangibleAssets1Details">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_a9fadbd8-050f-4350-8f47-01982dc1dfda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_a9fadbd8-050f-4350-8f47-01982dc1dfda" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bc1e349e-50a1-48f1-9946-3d1065f75969" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_bc1e349e-50a1-48f1-9946-3d1065f75969" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_9a2dcaef-7194-4fed-9fbf-3bb2c6e877d7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_9a2dcaef-7194-4fed-9fbf-3bb2c6e877d7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_a18c3c19-a825-4602-9cd9-bb60655f0dfb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_a18c3c19-a825-4602-9cd9-bb60655f0dfb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_2f1f7e91-dd05-48c8-b01f-32e124a52b59" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_2f1f7e91-dd05-48c8-b01f-32e124a52b59" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7b8d5b2e-50b0-469a-b774-ec92f5508006" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_7b8d5b2e-50b0-469a-b774-ec92f5508006" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aca22d7e-e365-4b0f-b6d7-0e38afea1898" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_f10f0af0-eade-4581-adf7-f00178b9e6fa" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aca22d7e-e365-4b0f-b6d7-0e38afea1898" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88e260b5-0f2f-4306-b0ad-513ae291cb9e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_aca22d7e-e365-4b0f-b6d7-0e38afea1898" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88e260b5-0f2f-4306-b0ad-513ae291cb9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88e260b5-0f2f-4306-b0ad-513ae291cb9e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88e260b5-0f2f-4306-b0ad-513ae291cb9e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_88e260b5-0f2f-4306-b0ad-513ae291cb9e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_88e260b5-0f2f-4306-b0ad-513ae291cb9e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_1318570b-145e-46c5-a56f-58c235b5fb62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_PatentsMember_1318570b-145e-46c5-a56f-58c235b5fb62" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_5efc319f-b785-4088-b26b-207fcf186116" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_CustomerContractsMember_5efc319f-b785-4088-b26b-207fcf186116" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_dad797d1-06c6-4928-9638-5989864dcb40" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_dad797d1-06c6-4928-9638-5989864dcb40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_d94f7cdc-8a75-4fa9-b9ca-c826968853c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_TrademarksMember_d94f7cdc-8a75-4fa9-b9ca-c826968853c5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_3c5e480c-433d-4407-a107-03e309c3340d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_TradeNamesMember_3c5e480c-433d-4407-a107-03e309c3340d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_3075c419-f15f-477f-bec6-d57d4c3e69c0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_3075c419-f15f-477f-bec6-d57d4c3e69c0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_878cd86e-c5e9-476a-b198-9e6c31469297" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_878cd86e-c5e9-476a-b198-9e6c31469297" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InProcessResearchAndDevelopmentMember_68ce218d-422a-46ae-a024-c0584363fd75" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InProcessResearchAndDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_faf3a55f-80e9-4a80-8bd4-f3f2b2f37cfa" xlink:to="loc_us-gaap_InProcessResearchAndDevelopmentMember_68ce218d-422a-46ae-a024-c0584363fd75" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesFutureEstimatedAmortizationExpenseDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesFutureEstimatedAmortizationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesFutureEstimatedAmortizationExpenseDetails" xlink:type="extended" id="id5c01d9290c244c4ab7535e25e2356ae_GeneralandSummaryofSignificantAccountingPoliciesFutureEstimatedAmortizationExpenseDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_d10b09c1-9684-4d46-a709-44526c1b811b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseNextTwelveMonths_d10b09c1-9684-4d46-a709-44526c1b811b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_4fc7aa1a-49a9-4b9d-8f68-f6c7b667b141" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearTwo_4fc7aa1a-49a9-4b9d-8f68-f6c7b667b141" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0b1fd276-68e4-4f21-bbee-37da92410792" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearThree_0b1fd276-68e4-4f21-bbee-37da92410792" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_19e839b0-1b2c-4147-bca4-2902eaa1aa0c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFour_19e839b0-1b2c-4147-bca4-2902eaa1aa0c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_768a9cab-b5d1-4a68-99f5-3ce9bc48da38" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseYearFive_768a9cab-b5d1-4a68-99f5-3ce9bc48da38" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive_0cdcf654-d381-40da-a515-6a78d8b82be5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAmortizationExpenseAfterYearFive_0cdcf654-d381-40da-a515-6a78d8b82be5" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_0fdbc365-9872-48ac-a24c-6fbe5a5a6fa0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_0fdbc365-9872-48ac-a24c-6fbe5a5a6fa0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_e409fb9c-2ec7-460c-93a5-9176132a9f75" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_fd25ca95-c0b5-4e09-9b0d-2bf4d310d57d" xlink:to="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_e409fb9c-2ec7-460c-93a5-9176132a9f75" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_82d9711d-f00e-4b9a-8b68-524580035b89" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAcquiredFiniteLivedIntangibleAssetByMajorClassTable_e409fb9c-2ec7-460c-93a5-9176132a9f75" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_82d9711d-f00e-4b9a-8b68-524580035b89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d9711d-f00e-4b9a-8b68-524580035b89_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_82d9711d-f00e-4b9a-8b68-524580035b89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_82d9711d-f00e-4b9a-8b68-524580035b89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_63d3608c-7c69-4b88-b344-f7ea7b3c7a65" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_82d9711d-f00e-4b9a-8b68-524580035b89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_63d3608c-7c69-4b88-b344-f7ea7b3c7a65" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesInvestmentsDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesInvestmentsDetails" xlink:type="extended" id="ia1faaf7382384dffb7ec356af246f277_GeneralandSummaryofSignificantAccountingPoliciesInvestmentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_ba2794c4-31ee-4422-b3dd-1ee569fe8bd6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_a5c46c1e-5a23-431b-ab19-a1fcfb4f8db1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_ba2794c4-31ee-4422-b3dd-1ee569fe8bd6" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_a5c46c1e-5a23-431b-ab19-a1fcfb4f8db1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_c3003860-d032-47dd-8999-87c0733c2ce5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_ba2794c4-31ee-4422-b3dd-1ee569fe8bd6" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_c3003860-d032-47dd-8999-87c0733c2ce5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_ceb4a8a5-897e-41b1-aa7d-ebfc4501e636" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_ba2794c4-31ee-4422-b3dd-1ee569fe8bd6" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_ceb4a8a5-897e-41b1-aa7d-ebfc4501e636" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_6c079923-21d9-40a7-abbd-9738b014daac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_ba2794c4-31ee-4422-b3dd-1ee569fe8bd6" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_6c079923-21d9-40a7-abbd-9738b014daac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_f87292e2-f90a-4ab1-8341-85b0fb1c418a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_6c079923-21d9-40a7-abbd-9738b014daac" xlink:to="loc_us-gaap_InvestmentTypeAxis_f87292e2-f90a-4ab1-8341-85b0fb1c418a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_f87292e2-f90a-4ab1-8341-85b0fb1c418a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_f87292e2-f90a-4ab1-8341-85b0fb1c418a" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_f87292e2-f90a-4ab1-8341-85b0fb1c418a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_2afdcbbd-892e-4364-b46c-47eeaa22c523" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_f87292e2-f90a-4ab1-8341-85b0fb1c418a" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_2afdcbbd-892e-4364-b46c-47eeaa22c523" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_a66eefbe-e597-4bc0-966e-cc7ff52fa5e7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShortTermInvestmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_2afdcbbd-892e-4364-b46c-47eeaa22c523" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_a66eefbe-e597-4bc0-966e-cc7ff52fa5e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongtermInvestmentsDomain_bddf82bd-7bf6-4999-bffe-e19a5f73d706" xlink:href="icui-20211231.xsd#icui_LongtermInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_2afdcbbd-892e-4364-b46c-47eeaa22c523" xlink:to="loc_icui_LongtermInvestmentsDomain_bddf82bd-7bf6-4999-bffe-e19a5f73d706" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesNetIncomePerShareDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#GeneralandSummaryofSignificantAccountingPoliciesNetIncomePerShareDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeneralandSummaryofSignificantAccountingPoliciesNetIncomePerShareDetails" xlink:type="extended" id="i971f75d3a26a403c8dc30eefd96b39c0_GeneralandSummaryofSignificantAccountingPoliciesNetIncomePerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_a68a24cd-f8b6-4b5a-8765-64e3a0a869eb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_NetIncomeLoss_a68a24cd-f8b6-4b5a-8765-64e3a0a869eb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_33f2d535-0f05-4031-a13b-3c5eb05bb599" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_33f2d535-0f05-4031-a13b-3c5eb05bb599" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_b1fe3c63-883c-4739-8f80-8ddd65d80da2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_WeightedAverageNumberDilutedSharesOutstandingAdjustment_b1fe3c63-883c-4739-8f80-8ddd65d80da2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_47761e4e-7eef-444e-839f-3c8912afb42b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_47761e4e-7eef-444e-839f-3c8912afb42b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_fc2e9975-dd60-486f-9962-ed80ea7c5c13" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_EarningsPerShareBasic_fc2e9975-dd60-486f-9962-ed80ea7c5c13" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_46ac474e-4cea-41b9-8eb2-b60cbd8a61c8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_EarningsPerShareDiluted_46ac474e-4cea-41b9-8eb2-b60cbd8a61c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_28498bbd-8841-4f21-996f-a886084cd694" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_28498bbd-8841-4f21-996f-a886084cd694" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_38f7b4ab-f1ce-4136-a1f6-bd9d14c0fed8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_639cd4e7-12a8-432a-bdb5-5cdd5d9c3dd8" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_38f7b4ab-f1ce-4136-a1f6-bd9d14c0fed8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1f47e962-b039-4069-b991-b0c3e5c5255a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfEarningsPerShareDilutedByCommonClassTable_38f7b4ab-f1ce-4136-a1f6-bd9d14c0fed8" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1f47e962-b039-4069-b991-b0c3e5c5255a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1f47e962-b039-4069-b991-b0c3e5c5255a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1f47e962-b039-4069-b991-b0c3e5c5255a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_1f47e962-b039-4069-b991-b0c3e5c5255a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_df5c8904-84de-4001-b34e-5c0b6b95cc85" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_1f47e962-b039-4069-b991-b0c3e5c5255a" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_df5c8904-84de-4001-b34e-5c0b6b95cc85" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AcquisitionsPursuitVascularTables" xlink:type="simple" xlink:href="icui-20211231.xsd#AcquisitionsPursuitVascularTables"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AcquisitionsPursuitVascularTables" xlink:type="extended" id="i5026d4466df34ed59424e09d924554eb_AcquisitionsPursuitVascularTables">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_57b35e04-831f-4fd3-9fe6-091e2d882654" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock_67076bb4-f61e-482c-83c6-646c5ff7232b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_57b35e04-831f-4fd3-9fe6-091e2d882654" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTextBlock_67076bb4-f61e-482c-83c6-646c5ff7232b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_9fae65fd-b297-4b54-9588-c31864a02431" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_57b35e04-831f-4fd3-9fe6-091e2d882654" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_9fae65fd-b297-4b54-9588-c31864a02431" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_ccf0fe67-41c3-4519-b902-a430845cf819" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_9fae65fd-b297-4b54-9588-c31864a02431" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_ccf0fe67-41c3-4519-b902-a430845cf819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ccf0fe67-41c3-4519-b902-a430845cf819_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ccf0fe67-41c3-4519-b902-a430845cf819" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ccf0fe67-41c3-4519-b902-a430845cf819_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4a9ff3a3-bdd7-4a66-b4f7-e4e79f11b193" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_ccf0fe67-41c3-4519-b902-a430845cf819" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4a9ff3a3-bdd7-4a66-b4f7-e4e79f11b193" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_81c3035f-1bc3-4648-a801-5699b61d3f3e" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4a9ff3a3-bdd7-4a66-b4f7-e4e79f11b193" xlink:to="loc_icui_PursuitVascularInc.Member_81c3035f-1bc3-4648-a801-5699b61d3f3e" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AcquisitionsTextDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#AcquisitionsTextDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AcquisitionsTextDetails" xlink:type="extended" id="i8f96e54d17b2479189b50792cbe13db4_AcquisitionsTextDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_b9a88792-1237-4755-aa6e-a0499c918d47" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_b9a88792-1237-4755-aa6e-a0499c918d47" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_60708386-0295-468a-8532-29e52bf17796" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_60708386-0295-468a-8532-29e52bf17796" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_0274679b-9d7d-451c-8bd1-8976706a7c41" xlink:href="icui-20211231.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:to="loc_icui_Contingentconsiderationgross_0274679b-9d7d-451c-8bd1-8976706a7c41" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_051715f4-ab44-4a49-817c-ab60ebde4dcb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_051715f4-ab44-4a49-817c-ab60ebde4dcb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5512131d-cedc-4f04-b133-ee3351310164" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_f3eb0451-f227-4046-8af0-8b993b78b229" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5512131d-cedc-4f04-b133-ee3351310164" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5d4107f0-95d2-4492-8560-64cf9c4362d7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_5512131d-cedc-4f04-b133-ee3351310164" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5d4107f0-95d2-4492-8560-64cf9c4362d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d4107f0-95d2-4492-8560-64cf9c4362d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5d4107f0-95d2-4492-8560-64cf9c4362d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d4107f0-95d2-4492-8560-64cf9c4362d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21c12abd-8d2a-46b0-aa68-211a9556bfa2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_5d4107f0-95d2-4492-8560-64cf9c4362d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21c12abd-8d2a-46b0-aa68-211a9556bfa2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_92baab59-ae00-48c0-9663-148006c07aa4" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21c12abd-8d2a-46b0-aa68-211a9556bfa2" xlink:to="loc_icui_PursuitVascularInc.Member_92baab59-ae00-48c0-9663-148006c07aa4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignDistibutorMember_406752a7-4c0e-4dcd-8324-c41495bee62f" xlink:href="icui-20211231.xsd#icui_ForeignDistibutorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21c12abd-8d2a-46b0-aa68-211a9556bfa2" xlink:to="loc_icui_ForeignDistibutorMember_406752a7-4c0e-4dcd-8324-c41495bee62f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_8f12d8d5-b694-4add-bfb3-64adaeeeca0b" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_21c12abd-8d2a-46b0-aa68-211a9556bfa2" xlink:to="loc_icui_PursuitVascularLLCMember_8f12d8d5-b694-4add-bfb3-64adaeeeca0b" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AcquisitionsPursuitVascularTableDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#AcquisitionsPursuitVascularTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AcquisitionsPursuitVascularTableDetails" xlink:type="extended" id="i2ae70560888c403c9e4ac8444eb0c05b_AcquisitionsPursuitVascularTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Paymenttoacquirebusinessnetofworkingcapitaladjustments_e4f78b5d-4b08-4b5a-aac5-7dd2b78758be" xlink:href="icui-20211231.xsd#icui_Paymenttoacquirebusinessnetofworkingcapitaladjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_icui_Paymenttoacquirebusinessnetofworkingcapitaladjustments_e4f78b5d-4b08-4b5a-aac5-7dd2b78758be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_893a64bc-a04f-499c-abad-9301dee402bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_893a64bc-a04f-499c-abad-9301dee402bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_bcc70f06-73a8-446c-834f-def446c52778" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferred1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_bcc70f06-73a8-446c-834f-def446c52778" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationAcquiredReceivablesFairValue_0aaf5894-32da-4386-ae79-23c3de7e7865" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationAcquiredReceivablesFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationAcquiredReceivablesFairValue_0aaf5894-32da-4386-ae79-23c3de7e7865" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_97f81b0a-4e3d-4059-9af4-79c414964879" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_97f81b0a-4e3d-4059-9af4-79c414964879" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_bbb2683d-cbf2-4d52-9a8d-8e28b85096ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_bbb2683d-cbf2-4d52-9a8d-8e28b85096ba" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_73be0025-2605-4a38-b7e8-98ced1634472" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_73be0025-2605-4a38-b7e8-98ced1634472" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_7c540868-c885-44ee-9f97-ab17f2d4306c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_7c540868-c885-44ee-9f97-ab17f2d4306c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_45f42ab5-cb42-4d2b-86ac-08350a34abe5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_45f42ab5-cb42-4d2b-86ac-08350a34abe5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_a84cbb97-d5d0-459e-8185-ca80760fa5fd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesOther_a84cbb97-d5d0-459e-8185-ca80760fa5fd" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_edb8af83-5351-48bf-bf92-7ea79e2da5cb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_edb8af83-5351-48bf-bf92-7ea79e2da5cb" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_03c5009d-e090-41d4-80dc-69c580f4a999" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_03c5009d-e090-41d4-80dc-69c580f4a999" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_149160d4-c3d9-438d-8bef-5a59ebf09944" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_149160d4-c3d9-438d-8bef-5a59ebf09944" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_f63e9d31-95e2-418f-89ee-17bad071a347" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_3c22b7e3-51e3-4248-9487-b6a9990aba6d" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_f63e9d31-95e2-418f-89ee-17bad071a347" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_0581b8a7-2b44-462a-95e8-bbc29d5a28d7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_f63e9d31-95e2-418f-89ee-17bad071a347" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_0581b8a7-2b44-462a-95e8-bbc29d5a28d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0581b8a7-2b44-462a-95e8-bbc29d5a28d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_0581b8a7-2b44-462a-95e8-bbc29d5a28d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0581b8a7-2b44-462a-95e8-bbc29d5a28d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1be31d5b-5131-42cc-b299-80ff3e2760bb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_0581b8a7-2b44-462a-95e8-bbc29d5a28d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1be31d5b-5131-42cc-b299-80ff3e2760bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_709dced6-e39c-4cee-9525-4dc26bbfc3c5" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1be31d5b-5131-42cc-b299-80ff3e2760bb" xlink:to="loc_icui_PursuitVascularInc.Member_709dced6-e39c-4cee-9525-4dc26bbfc3c5" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AcquisitionsPursuitVascularIntangibleDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#AcquisitionsPursuitVascularIntangibleDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AcquisitionsPursuitVascularIntangibleDetails" xlink:type="extended" id="ice81505568e14df19c96862be217587d_AcquisitionsPursuitVascularIntangibleDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_23e25766-5a18-4a77-bf23-e9975a34bb8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_edf8058a-0b7c-4a84-87b9-b4a1072f07b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_23e25766-5a18-4a77-bf23-e9975a34bb8a" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_edf8058a-0b7c-4a84-87b9-b4a1072f07b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3a879f52-2114-43b2-8412-9a2468753bb1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_23e25766-5a18-4a77-bf23-e9975a34bb8a" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_3a879f52-2114-43b2-8412-9a2468753bb1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_0e3c03dc-bf2f-4400-89e7-bfa1acf10b7d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsLineItems_23e25766-5a18-4a77-bf23-e9975a34bb8a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_0e3c03dc-bf2f-4400-89e7-bfa1acf10b7d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_81ada68c-0580-44f2-a917-643ecfbe8948" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_0e3c03dc-bf2f-4400-89e7-bfa1acf10b7d" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_81ada68c-0580-44f2-a917-643ecfbe8948" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81ada68c-0580-44f2-a917-643ecfbe8948_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_81ada68c-0580-44f2-a917-643ecfbe8948" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81ada68c-0580-44f2-a917-643ecfbe8948_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9edb395d-70e9-463a-acf3-e1a9524a3669" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_81ada68c-0580-44f2-a917-643ecfbe8948" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9edb395d-70e9-463a-acf3-e1a9524a3669" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_bc7b86fb-e255-4415-8049-8605962096d2" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9edb395d-70e9-463a-acf3-e1a9524a3669" xlink:to="loc_icui_PursuitVascularInc.Member_bc7b86fb-e255-4415-8049-8605962096d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ea4af82c-7a6f-48d7-b374-27b0914ac4ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsAcquiredAsPartOfBusinessCombinationTable_0e3c03dc-bf2f-4400-89e7-bfa1acf10b7d" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ea4af82c-7a6f-48d7-b374-27b0914ac4ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ea4af82c-7a6f-48d7-b374-27b0914ac4ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ea4af82c-7a6f-48d7-b374-27b0914ac4ba" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ea4af82c-7a6f-48d7-b374-27b0914ac4ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dc8034f8-edb0-432a-8f79-ec8fb164b3b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_ea4af82c-7a6f-48d7-b374-27b0914ac4ba" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dc8034f8-edb0-432a-8f79-ec8fb164b3b6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_177d0951-1359-41e3-a7b0-b11673f50894" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dc8034f8-edb0-432a-8f79-ec8fb164b3b6" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_177d0951-1359-41e3-a7b0-b11673f50894" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_be74d156-d319-4a57-b733-cdbfd8c6ac3f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dc8034f8-edb0-432a-8f79-ec8fb164b3b6" xlink:to="loc_us-gaap_TradeNamesMember_be74d156-d319-4a57-b733-cdbfd8c6ac3f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_4c95e8c9-0fcb-40c2-ae80-2ff07aa0ae1f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_dc8034f8-edb0-432a-8f79-ec8fb164b3b6" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_4c95e8c9-0fcb-40c2-ae80-2ff07aa0ae1f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AcquisitionsForeignInfusionSystemsSupplierDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#AcquisitionsForeignInfusionSystemsSupplierDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AcquisitionsForeignInfusionSystemsSupplierDetails" xlink:type="extended" id="i4af933c4ab2543a68b81d5a20c3963be_AcquisitionsForeignInfusionSystemsSupplierDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_9374c97e-af08-4a5d-8344-e2b7ae293116" xlink:href="icui-20211231.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_icui_Contingentconsiderationgross_9374c97e-af08-4a5d-8344-e2b7ae293116" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermContingentConsiderationGross_64f1772f-b9b9-4d13-bfd7-c6fa7571d9a8" xlink:href="icui-20211231.xsd#icui_ShortTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_icui_ShortTermContingentConsiderationGross_64f1772f-b9b9-4d13-bfd7-c6fa7571d9a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermContingentConsiderationGross_e61c000f-b32b-442b-9b07-6b606b85274e" xlink:href="icui-20211231.xsd#icui_LongTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_icui_LongTermContingentConsiderationGross_e61c000f-b32b-442b-9b07-6b606b85274e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_38d4a3d4-d027-4afd-93a4-b66ce323dc8e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_38d4a3d4-d027-4afd-93a4-b66ce323dc8e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationConsiderationCashHoldback_5875c9e6-9094-4481-abf4-c1ea04110748" xlink:href="icui-20211231.xsd#icui_BusinessCombinationConsiderationCashHoldback"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_icui_BusinessCombinationConsiderationCashHoldback_5875c9e6-9094-4481-abf4-c1ea04110748" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a696eb6e-8120-4e4b-b6a2-c1388e2a2286" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_5cc7dd2b-e640-47ee-994d-9f240a312343" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a696eb6e-8120-4e4b-b6a2-c1388e2a2286" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_bbae4c1f-196a-445e-b7a3-7cf14c993584" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_a696eb6e-8120-4e4b-b6a2-c1388e2a2286" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_bbae4c1f-196a-445e-b7a3-7cf14c993584" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbae4c1f-196a-445e-b7a3-7cf14c993584_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_bbae4c1f-196a-445e-b7a3-7cf14c993584" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bbae4c1f-196a-445e-b7a3-7cf14c993584_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_61d4c34d-281d-45af-b88b-afb4708420e3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_bbae4c1f-196a-445e-b7a3-7cf14c993584" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_61d4c34d-281d-45af-b88b-afb4708420e3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_ea77c5ee-f77f-4524-ae7d-89bd21a5991b" xlink:href="icui-20211231.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_61d4c34d-281d-45af-b88b-afb4708420e3" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_ea77c5ee-f77f-4524-ae7d-89bd21a5991b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationDetails1" xlink:type="simple" xlink:href="icui-20211231.xsd#RestructuringStrategicTransactionandIntegrationDetails1"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationDetails1" xlink:type="extended" id="i889ba9981e134d9883647c667eaa8bc4_RestructuringStrategicTransactionandIntegrationDetails1">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_641c0385-c7f9-497b-bd9c-2a98a8145787" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAccrualAdjustment1_92478776-bd65-4dd8-84e9-77ef328c43d2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringReserveAccrualAdjustment1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_641c0385-c7f9-497b-bd9c-2a98a8145787" xlink:to="loc_us-gaap_RestructuringReserveAccrualAdjustment1_92478776-bd65-4dd8-84e9-77ef328c43d2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RestructuringAdjustmentsSeveranceAndFacility_6fb68e56-0353-4d8d-b918-e70cd5af6fbd" xlink:href="icui-20211231.xsd#icui_RestructuringAdjustmentsSeveranceAndFacility"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_641c0385-c7f9-497b-bd9c-2a98a8145787" xlink:to="loc_icui_RestructuringAdjustmentsSeveranceAndFacility_6fb68e56-0353-4d8d-b918-e70cd5af6fbd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6182709b-4e98-41be-9c6f-e63a868061da" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_641c0385-c7f9-497b-bd9c-2a98a8145787" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6182709b-4e98-41be-9c6f-e63a868061da" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_dbf05479-c297-4d56-aa68-5021005a9112" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6182709b-4e98-41be-9c6f-e63a868061da" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_dbf05479-c297-4d56-aa68-5021005a9112" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_dbf05479-c297-4d56-aa68-5021005a9112_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_dbf05479-c297-4d56-aa68-5021005a9112" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_dbf05479-c297-4d56-aa68-5021005a9112_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_2c6976d0-83dc-4490-86eb-ab16f80ddfbb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_dbf05479-c297-4d56-aa68-5021005a9112" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_2c6976d0-83dc-4490-86eb-ab16f80ddfbb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FacilityClosingMember_c3c4e54a-49b9-4617-aaea-d24e22aea4b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FacilityClosingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_2c6976d0-83dc-4490-86eb-ab16f80ddfbb" xlink:to="loc_us-gaap_FacilityClosingMember_c3c4e54a-49b9-4617-aaea-d24e22aea4b0" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationDetails2" xlink:type="simple" xlink:href="icui-20211231.xsd#RestructuringStrategicTransactionandIntegrationDetails2"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationDetails2" xlink:type="extended" id="i090df861ef5f4cefa20b231c01f027dd_RestructuringStrategicTransactionandIntegrationDetails2">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_e761d2b8-c32b-4501-bbff-8943677cc319" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_RestructuringReserve_e761d2b8-c32b-4501-bbff-8943677cc319" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCosts_0c5b71a4-9afa-47f7-9697-89c477262f5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_RestructuringCosts_0c5b71a4-9afa-47f7-9697-89c477262f5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_5f2a02f5-473e-4850-9e18-8e183ac743d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_PaymentsForRestructuring_5f2a02f5-473e-4850-9e18-8e183ac743d8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveTranslationAdjustment_3f9ce30c-3da0-4265-a4ac-434340abeaff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringReserveTranslationAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_RestructuringReserveTranslationAdjustment_3f9ce30c-3da0-4265-a4ac-434340abeaff" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAccrualAdjustment1_f45e9dee-2d95-43b3-ba2c-b9bf0a399b54" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringReserveAccrualAdjustment1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_RestructuringReserveAccrualAdjustment1_f45e9dee-2d95-43b3-ba2c-b9bf0a399b54" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_8790be9f-4f8a-4b42-99e9-0fb1cf0ffdbb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_59145e0a-8648-4e0f-a609-3f6b7b943311" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_8790be9f-4f8a-4b42-99e9-0fb1cf0ffdbb" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_67e7d35f-c8cd-461a-b8c0-050e397e1687" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_8790be9f-4f8a-4b42-99e9-0fb1cf0ffdbb" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_67e7d35f-c8cd-461a-b8c0-050e397e1687" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_67e7d35f-c8cd-461a-b8c0-050e397e1687_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_67e7d35f-c8cd-461a-b8c0-050e397e1687" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_67e7d35f-c8cd-461a-b8c0-050e397e1687_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_bfb750fe-ad85-4e90-83d3-6575c1bebdfb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_67e7d35f-c8cd-461a-b8c0-050e397e1687" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_bfb750fe-ad85-4e90-83d3-6575c1bebdfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_957025f5-a363-41c4-bf4f-6ac0b3976ef0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_bfb750fe-ad85-4e90-83d3-6575c1bebdfb" xlink:to="loc_us-gaap_EmployeeSeveranceMember_957025f5-a363-41c4-bf4f-6ac0b3976ef0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SpecialTerminationBenefitsMember_5b40b5c8-a0db-4206-9623-2a730add452d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SpecialTerminationBenefitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_bfb750fe-ad85-4e90-83d3-6575c1bebdfb" xlink:to="loc_us-gaap_SpecialTerminationBenefitsMember_5b40b5c8-a0db-4206-9623-2a730add452d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FacilityClosingMember_3bb6a556-7d39-4faf-8707-9dbe9881cdd8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FacilityClosingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_bfb750fe-ad85-4e90-83d3-6575c1bebdfb" xlink:to="loc_us-gaap_FacilityClosingMember_3bb6a556-7d39-4faf-8707-9dbe9881cdd8" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregationofRevenueProductLineDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#RevenueDisaggregationofRevenueProductLineDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregationofRevenueProductLineDetails" xlink:type="extended" id="i19e96e9fe3fa4a52ad507bea5fd45436_RevenueDisaggregationofRevenueProductLineDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_c4b7cde9-5189-45e2-bef0-d3c31dc8bc74" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_1e1d833c-8323-4b79-abab-5aab9ec35848" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c4b7cde9-5189-45e2-bef0-d3c31dc8bc74" xlink:to="loc_us-gaap_Revenues_1e1d833c-8323-4b79-abab-5aab9ec35848" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Percentageofrevenue_ce17f8ef-e7b1-4053-bfbc-1e7fb40bdd0f" xlink:href="icui-20211231.xsd#icui_Percentageofrevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c4b7cde9-5189-45e2-bef0-d3c31dc8bc74" xlink:to="loc_icui_Percentageofrevenue_ce17f8ef-e7b1-4053-bfbc-1e7fb40bdd0f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_f050c84b-d2ac-4c2e-956f-84b03b409ebf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_c4b7cde9-5189-45e2-bef0-d3c31dc8bc74" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_f050c84b-d2ac-4c2e-956f-84b03b409ebf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_fba5e580-b566-4abc-9788-aea5862e57a8" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f050c84b-d2ac-4c2e-956f-84b03b409ebf" xlink:to="loc_srt_ProductOrServiceAxis_fba5e580-b566-4abc-9788-aea5862e57a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_fba5e580-b566-4abc-9788-aea5862e57a8_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_fba5e580-b566-4abc-9788-aea5862e57a8" xlink:to="loc_srt_ProductsAndServicesDomain_fba5e580-b566-4abc-9788-aea5862e57a8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_fba5e580-b566-4abc-9788-aea5862e57a8" xlink:to="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionConsumablesMember_bff4c654-9dde-48ef-bdb9-107c4ddc83c4" xlink:href="icui-20211231.xsd#icui_InfusionConsumablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:to="loc_icui_InfusionConsumablesMember_bff4c654-9dde-48ef-bdb9-107c4ddc83c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionSystemsMember_6a94d0f1-1173-43dc-b873-76332875be45" xlink:href="icui-20211231.xsd#icui_InfusionSystemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:to="loc_icui_InfusionSystemsMember_6a94d0f1-1173-43dc-b873-76332875be45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IVSolutionsMember_a84d03f6-079c-401c-83b4-668636556319" xlink:href="icui-20211231.xsd#icui_IVSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:to="loc_icui_IVSolutionsMember_a84d03f6-079c-401c-83b4-668636556319" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CriticalCareMember_8917d7ab-5790-4219-a324-5996bce7c5dd" xlink:href="icui-20211231.xsd#icui_CriticalCareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_7c9b333e-e2c8-41dd-841b-a2e9d7dee86b" xlink:to="loc_icui_CriticalCareMember_8917d7ab-5790-4219-a324-5996bce7c5dd" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregationofRevenuebyGeographyDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#RevenueDisaggregationofRevenuebyGeographyDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregationofRevenuebyGeographyDetails" xlink:type="extended" id="i9ac80483bda44d62a7cc03fca67b6af6_RevenueDisaggregationofRevenuebyGeographyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_9e03a600-2247-47c2-a697-ad92375ab191" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Percentoftotalrevenue_6975b757-a371-4f0e-976b-f78b64661129" xlink:href="icui-20211231.xsd#icui_Percentoftotalrevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_9e03a600-2247-47c2-a697-ad92375ab191" xlink:to="loc_icui_Percentoftotalrevenue_6975b757-a371-4f0e-976b-f78b64661129" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_a590dcaa-b80f-4b68-b01e-381243289f2c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_9e03a600-2247-47c2-a697-ad92375ab191" xlink:to="loc_us-gaap_Revenues_a590dcaa-b80f-4b68-b01e-381243289f2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_79283f46-b9a1-4ebf-b2b5-6e5170b7a754" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_9e03a600-2247-47c2-a697-ad92375ab191" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_79283f46-b9a1-4ebf-b2b5-6e5170b7a754" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_f2327687-3ba1-40d0-b4ae-87c7d23abf17" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_79283f46-b9a1-4ebf-b2b5-6e5170b7a754" xlink:to="loc_srt_StatementGeographicalAxis_f2327687-3ba1-40d0-b4ae-87c7d23abf17" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_f2327687-3ba1-40d0-b4ae-87c7d23abf17_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_f2327687-3ba1-40d0-b4ae-87c7d23abf17" xlink:to="loc_srt_SegmentGeographicalDomain_f2327687-3ba1-40d0-b4ae-87c7d23abf17_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_f2327687-3ba1-40d0-b4ae-87c7d23abf17" xlink:to="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_7c4b4273-23a5-4bc5-bcb2-40426a17e41e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:to="loc_us-gaap_EMEAMember_7c4b4273-23a5-4bc5-bcb2-40426a17e41e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherforeigncountriesMember_626cff77-3124-4a61-975c-624a33933b77" xlink:href="icui-20211231.xsd#icui_OtherforeigncountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:to="loc_icui_OtherforeigncountriesMember_626cff77-3124-4a61-975c-624a33933b77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignMember_0bed0b9e-b506-4cf7-b491-fbe7db516abf" xlink:href="icui-20211231.xsd#icui_ForeignMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:to="loc_icui_ForeignMember_0bed0b9e-b506-4cf7-b491-fbe7db516abf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_44935cba-880c-46b6-985d-1808ee970e5f" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:to="loc_country_US_44935cba-880c-46b6-985d-1808ee970e5f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalSalesDomain_e383f2e3-ef22-4f63-b235-6ee071e60388" xlink:href="icui-20211231.xsd#icui_InternationalSalesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_d2dbb542-e5b6-4b1f-a778-46e26f70b355" xlink:to="loc_icui_InternationalSalesDomain_e383f2e3-ef22-4f63-b235-6ee071e60388" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#RevenueContractLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="extended" id="i19512709623e430597c6b05a29d9d9c3_RevenueContractLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesLineItems_2cf71310-0509-436f-9b0c-573c0c4978f6" xlink:href="icui-20211231.xsd#icui_ContractassetandliabilitybalancesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_COntractLiabilityRollforwardRollForward_553b60be-69f3-499d-bfb7-04161c79e66a" xlink:href="icui-20211231.xsd#icui_COntractLiabilityRollforwardRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_2cf71310-0509-436f-9b0c-573c0c4978f6" xlink:to="loc_icui_COntractLiabilityRollforwardRollForward_553b60be-69f3-499d-bfb7-04161c79e66a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_9051a92e-df9b-477f-b4c4-ea79a9b655c5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_COntractLiabilityRollforwardRollForward_553b60be-69f3-499d-bfb7-04161c79e66a" xlink:to="loc_us-gaap_ContractWithCustomerLiability_9051a92e-df9b-477f-b4c4-ea79a9b655c5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_5833759c-fa83-402d-b9a4-706c0f9bf271" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_COntractLiabilityRollforwardRollForward_553b60be-69f3-499d-bfb7-04161c79e66a" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_5833759c-fa83-402d-b9a4-706c0f9bf271" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueAdditions_c3f18b96-a30e-4a5a-9813-77166de458e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredRevenueAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_COntractLiabilityRollforwardRollForward_553b60be-69f3-499d-bfb7-04161c79e66a" xlink:to="loc_us-gaap_DeferredRevenueAdditions_c3f18b96-a30e-4a5a-9813-77166de458e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_c364101d-ee51-4a6b-b8ed-291cd976c405" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesTable_66d914dc-d92f-48b9-bbbf-5dc2417f7308" xlink:href="icui-20211231.xsd#icui_ContractassetandliabilitybalancesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_2cf71310-0509-436f-9b0c-573c0c4978f6" xlink:to="loc_icui_ContractassetandliabilitybalancesTable_66d914dc-d92f-48b9-bbbf-5dc2417f7308" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_728bdeb9-929f-4d68-935b-1f152372ce89" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ContractassetandliabilitybalancesTable_66d914dc-d92f-48b9-bbbf-5dc2417f7308" xlink:to="loc_srt_ProductOrServiceAxis_728bdeb9-929f-4d68-935b-1f152372ce89" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_728bdeb9-929f-4d68-935b-1f152372ce89_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_728bdeb9-929f-4d68-935b-1f152372ce89" xlink:to="loc_srt_ProductsAndServicesDomain_728bdeb9-929f-4d68-935b-1f152372ce89_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_1d02e4dd-8f52-4bb0-ade6-e3e621ee3522" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_728bdeb9-929f-4d68-935b-1f152372ce89" xlink:to="loc_srt_ProductsAndServicesDomain_1d02e4dd-8f52-4bb0-ade6-e3e621ee3522" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_c0bc4a3f-3311-4f98-842c-7271389a52c7" xlink:href="icui-20211231.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1d02e4dd-8f52-4bb0-ade6-e3e621ee3522" xlink:to="loc_icui_EquipmentrevenueMember_c0bc4a3f-3311-4f98-842c-7271389a52c7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_727fd294-6336-4f15-96f2-25d67f49448d" xlink:href="icui-20211231.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_1d02e4dd-8f52-4bb0-ade6-e3e621ee3522" xlink:to="loc_icui_SoftwarerevenueMember_727fd294-6336-4f15-96f2-25d67f49448d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueContractLiabilitiesTextDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#RevenueContractLiabilitiesTextDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueContractLiabilitiesTextDetails" xlink:type="extended" id="i901977201a6949d2842fcf2d6fc80d7d_RevenueContractLiabilitiesTextDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesLineItems_9148698e-62fa-4bd9-89b3-75291de0ebec" xlink:href="icui-20211231.xsd#icui_ContractassetandliabilitybalancesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_0ff2b126-3324-400a-8733-711860a8966a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_9148698e-62fa-4bd9-89b3-75291de0ebec" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityRevenueRecognized_0ff2b126-3324-400a-8733-711860a8966a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_d5413aff-ae5f-4f50-bd06-9c393a05aa35" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_9148698e-62fa-4bd9-89b3-75291de0ebec" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_d5413aff-ae5f-4f50-bd06-9c393a05aa35" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesTable_5e238cda-a8dd-4d37-89c7-55431a39411e" xlink:href="icui-20211231.xsd#icui_ContractassetandliabilitybalancesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_9148698e-62fa-4bd9-89b3-75291de0ebec" xlink:to="loc_icui_ContractassetandliabilitybalancesTable_5e238cda-a8dd-4d37-89c7-55431a39411e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_0a964030-9b18-46b8-b8a2-5220b413eb47" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ContractassetandliabilitybalancesTable_5e238cda-a8dd-4d37-89c7-55431a39411e" xlink:to="loc_srt_ProductOrServiceAxis_0a964030-9b18-46b8-b8a2-5220b413eb47" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_0a964030-9b18-46b8-b8a2-5220b413eb47_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_0a964030-9b18-46b8-b8a2-5220b413eb47" xlink:to="loc_srt_ProductsAndServicesDomain_0a964030-9b18-46b8-b8a2-5220b413eb47_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_92468c7f-1d72-4b64-b272-8997c7b61efa" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_0a964030-9b18-46b8-b8a2-5220b413eb47" xlink:to="loc_srt_ProductsAndServicesDomain_92468c7f-1d72-4b64-b272-8997c7b61efa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_419d9707-e026-4661-ad03-ef5c97a541c9" xlink:href="icui-20211231.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_92468c7f-1d72-4b64-b272-8997c7b61efa" xlink:to="loc_icui_EquipmentrevenueMember_419d9707-e026-4661-ad03-ef5c97a541c9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_dfd3fbe4-a895-4382-8d0c-88dfa712eb74" xlink:href="icui-20211231.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_92468c7f-1d72-4b64-b272-8997c7b61efa" xlink:to="loc_icui_SoftwarerevenueMember_dfd3fbe4-a895-4382-8d0c-88dfa712eb74" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#LeasesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesDetails" xlink:type="extended" id="if6a564b1254344be9beeac3b9ab3d38f_LeasesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_c4b761bf-37a7-4598-a822-49187144d3be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Optiontoextendinyears_3a164583-6108-45c6-a672-8f55aeaa5cfb" xlink:href="icui-20211231.xsd#icui_Optiontoextendinyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_c4b761bf-37a7-4598-a822-49187144d3be" xlink:to="loc_icui_Optiontoextendinyears_3a164583-6108-45c6-a672-8f55aeaa5cfb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_82779e3d-46b7-4b81-bf9b-b68a68f47eb7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_c4b761bf-37a7-4598-a822-49187144d3be" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_82779e3d-46b7-4b81-bf9b-b68a68f47eb7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_66102017-1f14-4b4e-a428-9919b715ab5f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_c4b761bf-37a7-4598-a822-49187144d3be" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_66102017-1f14-4b4e-a428-9919b715ab5f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_66102017-1f14-4b4e-a428-9919b715ab5f" xlink:to="loc_srt_RangeAxis_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc" xlink:to="loc_srt_RangeMember_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_0a0acd3e-312f-4e5a-aef6-6de4fa51d7ba" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_ed5015d9-3f36-4196-9d59-9a3bdda0c7cc" xlink:to="loc_srt_RangeMember_0a0acd3e-312f-4e5a-aef6-6de4fa51d7ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_704e7962-445d-4eda-a5cb-9f78f82234e4" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0a0acd3e-312f-4e5a-aef6-6de4fa51d7ba" xlink:to="loc_srt_MinimumMember_704e7962-445d-4eda-a5cb-9f78f82234e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_e02cd580-00a9-4f5d-8373-84c5938e3173" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_0a0acd3e-312f-4e5a-aef6-6de4fa51d7ba" xlink:to="loc_srt_MaximumMember_e02cd580-00a9-4f5d-8373-84c5938e3173" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ShareBasedAwardStockOptionPlansDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#ShareBasedAwardStockOptionPlansDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ShareBasedAwardStockOptionPlansDetails" xlink:type="extended" id="ib64d1fddbeee46b9ac0a5a4115e6e711_ShareBasedAwardStockOptionPlansDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:href="icui-20211231.xsd#icui_StockIncentivePlansLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_58fd230d-3ada-478b-872a-5c06614410a1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_58fd230d-3ada-478b-872a-5c06614410a1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_fd980ffc-0a3a-42ea-9ef3-335f2ff5ecfe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized_fd980ffc-0a3a-42ea-9ef3-335f2ff5ecfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Sharestransferredfromsupersededplan_bda14d69-f8f8-4d9a-a0c7-4ca71ee93211" xlink:href="icui-20211231.xsd#icui_Sharestransferredfromsupersededplan"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:to="loc_icui_Sharestransferredfromsupersededplan_bda14d69-f8f8-4d9a-a0c7-4ca71ee93211" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_062b08f6-2782-4b8b-b86b-a5537168ac03" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_062b08f6-2782-4b8b-b86b-a5537168ac03" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_StockIncentivePlansTable_a143d03d-aaf7-497b-8ee9-72432479ccb4" xlink:href="icui-20211231.xsd#icui_StockIncentivePlansTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_StockIncentivePlansLineItems_e9dcabfe-2dc9-4a42-8d57-2b0e7fc615d4" xlink:to="loc_icui_StockIncentivePlansTable_a143d03d-aaf7-497b-8ee9-72432479ccb4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_df719b4d-4abb-443f-b2cf-6439bc52b282" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_StockIncentivePlansTable_a143d03d-aaf7-497b-8ee9-72432479ccb4" xlink:to="loc_us-gaap_AwardTypeAxis_df719b4d-4abb-443f-b2cf-6439bc52b282" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_df719b4d-4abb-443f-b2cf-6439bc52b282_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_df719b4d-4abb-443f-b2cf-6439bc52b282" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_df719b4d-4abb-443f-b2cf-6439bc52b282_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54efda05-001a-49f2-a98a-24139a1424b0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_df719b4d-4abb-443f-b2cf-6439bc52b282" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54efda05-001a-49f2-a98a-24139a1424b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_8306b634-4686-4100-b320-805b5ffcfbf8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54efda05-001a-49f2-a98a-24139a1424b0" xlink:to="loc_us-gaap_EmployeeStockOptionMember_8306b634-4686-4100-b320-805b5ffcfbf8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_46db19f9-387b-485c-b7d0-9b1d437f717f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_54efda05-001a-49f2-a98a-24139a1424b0" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_46db19f9-387b-485c-b7d0-9b1d437f717f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_b76405f2-ad71-4ff8-9d08-760008c9f3a2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_StockIncentivePlansTable_a143d03d-aaf7-497b-8ee9-72432479ccb4" xlink:to="loc_us-gaap_PlanNameAxis_b76405f2-ad71-4ff8-9d08-760008c9f3a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b76405f2-ad71-4ff8-9d08-760008c9f3a2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_b76405f2-ad71-4ff8-9d08-760008c9f3a2" xlink:to="loc_us-gaap_PlanNameDomain_b76405f2-ad71-4ff8-9d08-760008c9f3a2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_206456c4-41d0-414c-a316-afd399c83710" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_b76405f2-ad71-4ff8-9d08-760008c9f3a2" xlink:to="loc_us-gaap_PlanNameDomain_206456c4-41d0-414c-a316-afd399c83710" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_A2011PlanMember_e139f772-1e1e-484c-9590-a6a7b09b07a3" xlink:href="icui-20211231.xsd#icui_A2011PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_206456c4-41d0-414c-a316-afd399c83710" xlink:to="loc_icui_A2011PlanMember_e139f772-1e1e-484c-9590-a6a7b09b07a3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_A2003PlanMember_0a415448-270a-40b1-b896-bd9bd720c5fa" xlink:href="icui-20211231.xsd#icui_A2003PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_206456c4-41d0-414c-a316-afd399c83710" xlink:to="loc_icui_A2003PlanMember_0a415448-270a-40b1-b896-bd9bd720c5fa" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ShareBasedAwardStockOptionsGrantedandValuationDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#ShareBasedAwardStockOptionsGrantedandValuationDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ShareBasedAwardStockOptionsGrantedandValuationDetails" xlink:type="extended" id="i8fda3967b06b43dbaaca453c5c26fc06_ShareBasedAwardStockOptionsGrantedandValuationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_fe85bf0b-5e05-4558-bf70-b9ded66f6c0d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_fe85bf0b-5e05-4558-bf70-b9ded66f6c0d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Timebasedoptionsgrantdatefairvalue_e94fe7e3-bea8-40a2-bbfc-2deb05e152dc" xlink:href="icui-20211231.xsd#icui_Timebasedoptionsgrantdatefairvalue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_icui_Timebasedoptionsgrantdatefairvalue_e94fe7e3-bea8-40a2-bbfc-2deb05e152dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_46efe5c6-c427-4b2f-8ac8-c0903270fab2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_46efe5c6-c427-4b2f-8ac8-c0903270fab2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_869b6672-7548-47e5-aae9-d68f7adefb72" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_869b6672-7548-47e5-aae9-d68f7adefb72" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_ad25d547-ba6a-4291-8738-0df35a593449" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_ad25d547-ba6a-4291-8738-0df35a593449" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e01c2b4d-7edf-4d39-8cb2-25b1580d600e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_e01c2b4d-7edf-4d39-8cb2-25b1580d600e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_0c3a7946-012c-436d-9c34-fa8b5e89ef4c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_0c3a7946-012c-436d-9c34-fa8b5e89ef4c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_ce249b3b-400e-4850-b8ac-671828ea4196" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_ce249b3b-400e-4850-b8ac-671828ea4196" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_af1f3418-4a15-4c47-ab83-a186e4a93f06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_de5589b5-8cc3-4d37-8197-a3e38263ed3a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_af1f3418-4a15-4c47-ab83-a186e4a93f06" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_b3f7d965-2858-42f2-93f6-eb397e7adc52" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_af1f3418-4a15-4c47-ab83-a186e4a93f06" xlink:to="loc_us-gaap_PlanNameAxis_b3f7d965-2858-42f2-93f6-eb397e7adc52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_b3f7d965-2858-42f2-93f6-eb397e7adc52_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_b3f7d965-2858-42f2-93f6-eb397e7adc52" xlink:to="loc_us-gaap_PlanNameDomain_b3f7d965-2858-42f2-93f6-eb397e7adc52_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_e1b5ac3a-b04e-4d6b-9719-412e13205cce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_b3f7d965-2858-42f2-93f6-eb397e7adc52" xlink:to="loc_us-gaap_PlanNameDomain_e1b5ac3a-b04e-4d6b-9719-412e13205cce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_A2011PlanMember_dc1d5007-938e-4f57-933e-630031db5ca8" xlink:href="icui-20211231.xsd#icui_A2011PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_e1b5ac3a-b04e-4d6b-9719-412e13205cce" xlink:to="loc_icui_A2011PlanMember_dc1d5007-938e-4f57-933e-630031db5ca8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_A2003PlanMember_e76abbce-e403-4fcd-b73e-fd2b5144ec5a" xlink:href="icui-20211231.xsd#icui_A2003PlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_e1b5ac3a-b04e-4d6b-9719-412e13205cce" xlink:to="loc_icui_A2003PlanMember_e76abbce-e403-4fcd-b73e-fd2b5144ec5a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_c71e8fcf-9910-44c6-b879-c3a9901a0c6a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_af1f3418-4a15-4c47-ab83-a186e4a93f06" xlink:to="loc_us-gaap_AwardTypeAxis_c71e8fcf-9910-44c6-b879-c3a9901a0c6a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c71e8fcf-9910-44c6-b879-c3a9901a0c6a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_c71e8fcf-9910-44c6-b879-c3a9901a0c6a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_c71e8fcf-9910-44c6-b879-c3a9901a0c6a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d66b4d8-ff27-4932-8b4d-58149d8d4ab9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_c71e8fcf-9910-44c6-b879-c3a9901a0c6a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d66b4d8-ff27-4932-8b4d-58149d8d4ab9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimebasedstockoptionMember_9f2a434a-4b8b-46ad-b2fc-f24daeade7e6" xlink:href="icui-20211231.xsd#icui_TimebasedstockoptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d66b4d8-ff27-4932-8b4d-58149d8d4ab9" xlink:to="loc_icui_TimebasedstockoptionMember_9f2a434a-4b8b-46ad-b2fc-f24daeade7e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_8fdd8fe3-127e-4e96-90c7-e7dd614137aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_8d66b4d8-ff27-4932-8b4d-58149d8d4ab9" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_8fdd8fe3-127e-4e96-90c7-e7dd614137aa" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ShareBasedAwardStockOptionActivityDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#ShareBasedAwardStockOptionActivityDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ShareBasedAwardStockOptionActivityDetails" xlink:type="extended" id="i2e8e17d5c7bb406c9ac6a88b419b8428_ShareBasedAwardStockOptionActivityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_70083047-ede1-409f-b83e-bc0739ebfcc5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_70083047-ede1-409f-b83e-bc0739ebfcc5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_51bd39b5-9c88-4fef-8dcd-1da99d024f20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_51bd39b5-9c88-4fef-8dcd-1da99d024f20" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_b4c58420-4c54-425b-8f97-4da7e65308af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_b4c58420-4c54-425b-8f97-4da7e65308af" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares_f6957bf2-f559-451e-8736-1165209fa1f0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedNumberOfShares_f6957bf2-f559-451e-8736-1165209fa1f0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_bea95758-edc3-4599-9a7f-90d09d5ee3ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_9fe469ee-f9bc-4a66-a7da-8c1139d78a08" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_9fe469ee-f9bc-4a66-a7da-8c1139d78a08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber_322376e2-943e-4d10-af78-1c1a9c2799e4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestExercisableNumber_322376e2-943e-4d10-af78-1c1a9c2799e4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_06cc6ba8-59df-4acb-8321-cb182fee76f7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_06cc6ba8-59df-4acb-8321-cb182fee76f7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_9f570060-027a-4f2f-ae97-ea1e163f2f0f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_9f570060-027a-4f2f-ae97-ea1e163f2f0f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_6117838b-c547-43c2-90af-72132a5a7657" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExercisesInPeriodWeightedAverageExercisePrice_6117838b-c547-43c2-90af-72132a5a7657" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue_3e67e3e3-3ed9-4b33-b093-e5f37792eaf4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedOptionsForfeitedWeightedAverageGrantDateFairValue_3e67e3e3-3ed9-4b33-b093-e5f37792eaf4" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_d113bf8e-5c2b-4d61-b039-0fad5392da00" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_37451acb-3ad0-4c65-a2fa-73b1eabf317f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_37451acb-3ad0-4c65-a2fa-73b1eabf317f" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_41b0d2f0-3ad1-4c63-ada9-02f7f68c838d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageExercisePrice_41b0d2f0-3ad1-4c63-ada9-02f7f68c838d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_2ee57938-4f5a-4f3c-bd0c-410950dc0c8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_2ee57938-4f5a-4f3c-bd0c-410950dc0c8b" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_4382b97b-8b58-4750-96ca-dd8f3117fc3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableWeightedAverageRemainingContractualTerm1_4382b97b-8b58-4750-96ca-dd8f3117fc3c" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_6244b9f4-424b-4b33-9977-83644923acdb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedAverageRemainingContractualTerm1_6244b9f4-424b-4b33-9977-83644923acdb" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_a42cb44b-beee-49d0-8013-613fa8a07eb1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_a42cb44b-beee-49d0-8013-613fa8a07eb1" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_ac119be7-da2b-4753-a010-0f1281c65a2f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_ac119be7-da2b-4753-a010-0f1281c65a2f" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_2910b010-f5fd-48d1-bcf4-775605306425" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingAggregateIntrinsicValue_2910b010-f5fd-48d1-bcf4-775605306425" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fab86346-a9bb-4527-8a9f-b5edf57656f5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_53fb14b2-5983-4a31-ae57-00689229803a" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fab86346-a9bb-4527-8a9f-b5edf57656f5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_a0136923-4107-482a-8cb8-583f50ac718d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_fab86346-a9bb-4527-8a9f-b5edf57656f5" xlink:to="loc_us-gaap_AwardTypeAxis_a0136923-4107-482a-8cb8-583f50ac718d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a0136923-4107-482a-8cb8-583f50ac718d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_a0136923-4107-482a-8cb8-583f50ac718d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_a0136923-4107-482a-8cb8-583f50ac718d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6244c363-4dc4-41e5-a30b-eafd2c1d001f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_a0136923-4107-482a-8cb8-583f50ac718d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6244c363-4dc4-41e5-a30b-eafd2c1d001f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeStockOptionMember_40d47416-39a8-412c-be33-ba237ade23bb" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_6244c363-4dc4-41e5-a30b-eafd2c1d001f" xlink:to="loc_us-gaap_EmployeeStockOptionMember_40d47416-39a8-412c-be33-ba237ade23bb" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ShareBasedAwardRSUandPRSUDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#ShareBasedAwardRSUandPRSUDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ShareBasedAwardRSUandPRSUDetails" xlink:type="extended" id="i58e5a6dab20d446b96968549ddd3ac79_ShareBasedAwardRSUandPRSUDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_2575ea4d-037c-476b-9149-544be5ff5962" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_2575ea4d-037c-476b-9149-544be5ff5962" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PerformanceSharesEarned_d8fc194c-d0cb-4416-a7b6-c04715027752" xlink:href="icui-20211231.xsd#icui_PerformanceSharesEarned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_icui_PerformanceSharesEarned_d8fc194c-d0cb-4416-a7b6-c04715027752" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_9c1a3876-c554-40fb-84fa-56a212957125" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_9c1a3876-c554-40fb-84fa-56a212957125" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Grantdatefairvalueperformancerestrictedstockunits_49daa903-3fc1-4d4a-b64d-75cde174ca0a" xlink:href="icui-20211231.xsd#icui_Grantdatefairvalueperformancerestrictedstockunits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_icui_Grantdatefairvalueperformancerestrictedstockunits_49daa903-3fc1-4d4a-b64d-75cde174ca0a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Grantdatefairvalueofrestrictedstockunitsgranted_354eb5d1-7936-4e52-b527-14ae850b44cd" xlink:href="icui-20211231.xsd#icui_Grantdatefairvalueofrestrictedstockunitsgranted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_icui_Grantdatefairvalueofrestrictedstockunitsgranted_354eb5d1-7936-4e52-b527-14ae850b44cd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_eb0bee38-aefa-4433-824b-0dd8daf78abe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueVested_eb0bee38-aefa-4433-824b-0dd8daf78abe" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ModifiedPRSUIncrementalExpense_2e0e0537-acbd-411d-a8af-9eee26f17c27" xlink:href="icui-20211231.xsd#icui_ModifiedPRSUIncrementalExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_icui_ModifiedPRSUIncrementalExpense_2e0e0537-acbd-411d-a8af-9eee26f17c27" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3ac00d23-be41-49c6-91a2-a339117b45e4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_230b90e7-5e46-4c58-ab48-9d0d7177747c" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3ac00d23-be41-49c6-91a2-a339117b45e4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3ac00d23-be41-49c6-91a2-a339117b45e4" xlink:to="loc_us-gaap_AwardTypeAxis_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d193992d-3cf9-4d91-a759-2b603c013cf6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_25b0196c-6a6a-41ec-a1fd-9a0f2bd06742" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d193992d-3cf9-4d91-a759-2b603c013cf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PerformanceRestrictedStockUnitsPRSUsMember_4fe37f10-e1b1-4ca0-bc26-cbeb4678b9b6" xlink:href="icui-20211231.xsd#icui_PerformanceRestrictedStockUnitsPRSUsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d193992d-3cf9-4d91-a759-2b603c013cf6" xlink:to="loc_icui_PerformanceRestrictedStockUnitsPRSUsMember_4fe37f10-e1b1-4ca0-bc26-cbeb4678b9b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_241f4a64-70e7-43ef-aed0-f229b3078d7c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d193992d-3cf9-4d91-a759-2b603c013cf6" xlink:to="loc_us-gaap_PerformanceSharesMember_241f4a64-70e7-43ef-aed0-f229b3078d7c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_de2e1d3b-5fe1-4a4c-956b-c5f1a74fd727" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_d193992d-3cf9-4d91-a759-2b603c013cf6" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_de2e1d3b-5fe1-4a4c-956b-c5f1a74fd727" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/ShareBasedAwardRSUandPRSURollforwardDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#ShareBasedAwardRSUandPRSURollforwardDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/ShareBasedAwardRSUandPRSURollforwardDetails" xlink:type="extended" id="i9fcc8805d1a349d6a67a2e8a69601567_ShareBasedAwardRSUandPRSURollforwardDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_005c6dea-33eb-49e9-b49f-6f3e68e8d4c3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_005c6dea-33eb-49e9-b49f-6f3e68e8d4c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_54f64d2e-90f5-4f07-9799-cd2e04d1e614" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_54f64d2e-90f5-4f07-9799-cd2e04d1e614" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Changeinunitsduetoperformanceexpectations_8a623c21-7085-4745-8f80-91c78873ae90" xlink:href="icui-20211231.xsd#icui_Changeinunitsduetoperformanceexpectations"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_icui_Changeinunitsduetoperformanceexpectations_8a623c21-7085-4745-8f80-91c78873ae90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceExpectationAdditionsIntrinsicValue_70bbaf69-67ae-4bf5-abb2-5a0b1a75602a" xlink:href="icui-20211231.xsd#icui_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceExpectationAdditionsIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_icui_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPerformanceExpectationAdditionsIntrinsicValue_70bbaf69-67ae-4bf5-abb2-5a0b1a75602a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_129e8eac-6e3d-43cb-a343-22f262ca7de1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_129e8eac-6e3d-43cb-a343-22f262ca7de1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0ac0ffe3-e9e9-4b11-83f5-bfacbefb768c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_0ac0ffe3-e9e9-4b11-83f5-bfacbefb768c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_d513bce4-0dc5-46f1-850e-04af633e96c6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_d513bce4-0dc5-46f1-850e-04af633e96c6" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodIntrinsicValue_6408eb8e-0bec-49dd-b388-dff672387ee7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodIntrinsicValue_6408eb8e-0bec-49dd-b388-dff672387ee7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_51d838c2-3730-43bb-9a73-934e71a6eefd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_51d838c2-3730-43bb-9a73-934e71a6eefd" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresIntrinsicValue_721aec4f-4c13-4e76-ac84-6d218c79f040" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresIntrinsicValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresIntrinsicValue_721aec4f-4c13-4e76-ac84-6d218c79f040" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_acb38243-b9d1-487e-b7e6-ef588ad76f03" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsOutstandingWeightedAverageRemainingContractualTerms_acb38243-b9d1-487e-b7e6-ef588ad76f03" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested_151ba53f-7772-41cf-93a6-2ec12fa1dbdc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardEquityInstrumentsOtherThanOptionsAggregateIntrinsicValueNonvested_151ba53f-7772-41cf-93a6-2ec12fa1dbdc" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_83773412-6a27-4a30-9f00-5dbf40fec515" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_36265960-1f06-429d-aed8-f3561b6e031d" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_83773412-6a27-4a30-9f00-5dbf40fec515" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_806a3fe4-b4c3-495c-8299-0816b054675b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_83773412-6a27-4a30-9f00-5dbf40fec515" xlink:to="loc_us-gaap_AwardTypeAxis_806a3fe4-b4c3-495c-8299-0816b054675b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_806a3fe4-b4c3-495c-8299-0816b054675b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_806a3fe4-b4c3-495c-8299-0816b054675b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_806a3fe4-b4c3-495c-8299-0816b054675b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cdcb6780-7daf-4305-8602-1ea5142f5805" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_806a3fe4-b4c3-495c-8299-0816b054675b" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cdcb6780-7daf-4305-8602-1ea5142f5805" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RestrictedStockAndPerformanceRestrictedStockUnitsMember_b875b2f5-af9f-4a6c-8805-b5c04607e7f3" xlink:href="icui-20211231.xsd#icui_RestrictedStockAndPerformanceRestrictedStockUnitsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_cdcb6780-7daf-4305-8602-1ea5142f5805" xlink:to="loc_icui_RestrictedStockAndPerformanceRestrictedStockUnitsMember_b875b2f5-af9f-4a6c-8805-b5c04607e7f3" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativesandHedgingActivitiesDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#DerivativesandHedgingActivitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativesandHedgingActivitiesDetails" xlink:type="extended" id="ife7d4b4fa2934ca6883236e4f7c79954_DerivativesandHedgingActivitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeForwardExchangeRate1_8eeebdd7-8aff-4283-8ddb-4a2397ccac96" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeForwardExchangeRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_DerivativeForwardExchangeRate1_8eeebdd7-8aff-4283-8ddb-4a2397ccac96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotionalAmount_ff7b3e83-1bdb-47bf-a25c-4e4c7439117b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssetNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_DerivativeAssetNotionalAmount_ff7b3e83-1bdb-47bf-a25c-4e4c7439117b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityNotionalAmount_f8ae0bdb-67ab-474e-9164-f79aafb1d0e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilityNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_DerivativeLiabilityNotionalAmount_f8ae0bdb-67ab-474e-9164-f79aafb1d0e1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_d6522698-b415-4803-8a47-64646876e0e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_d6522698-b415-4803-8a47-64646876e0e1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_DerivativeInterestRateFloor_73ae46ef-a428-47b2-a0d0-0e17327f4177" xlink:href="icui-20211231.xsd#icui_DerivativeInterestRateFloor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_icui_DerivativeInterestRateFloor_73ae46ef-a428-47b2-a0d0-0e17327f4177" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_190961fa-59e9-42e2-bf5b-eec371ad4f7f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_190961fa-59e9-42e2-bf5b-eec371ad4f7f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_4f0329f5-0bd0-4aad-a941-26a51793380f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_4f0329f5-0bd0-4aad-a941-26a51793380f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_8eed295c-b3c9-4e02-adcc-aebf81581e4f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_9c35f56b-8732-40be-84c9-1a60c6dee34a" xlink:to="loc_us-gaap_DerivativeTable_8eed295c-b3c9-4e02-adcc-aebf81581e4f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_4ec07973-4981-47a2-9925-8379344d3252" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_8eed295c-b3c9-4e02-adcc-aebf81581e4f" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_4ec07973-4981-47a2-9925-8379344d3252" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4ec07973-4981-47a2-9925-8379344d3252_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_4ec07973-4981-47a2-9925-8379344d3252" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4ec07973-4981-47a2-9925-8379344d3252_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_4ec07973-4981-47a2-9925-8379344d3252" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge1Member_d1f70b6f-26c0-47fc-9a65-d7c638baf8b1" xlink:href="icui-20211231.xsd#icui_Hedge1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_Hedge1Member_d1f70b6f-26c0-47fc-9a65-d7c638baf8b1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge2Member_5f9075cc-5cc4-4f60-9aca-f24afd99b0c9" xlink:href="icui-20211231.xsd#icui_Hedge2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_Hedge2Member_5f9075cc-5cc4-4f60-9aca-f24afd99b0c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge3MemberMember_0e419e68-b913-4f28-aedb-71722df29ba6" xlink:href="icui-20211231.xsd#icui_Hedge3MemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_Hedge3MemberMember_0e419e68-b913-4f28-aedb-71722df29ba6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge4Member_021d924d-21aa-4706-b01d-df2cfdf07e70" xlink:href="icui-20211231.xsd#icui_Hedge4Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_Hedge4Member_021d924d-21aa-4706-b01d-df2cfdf07e70" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge5Member_6dadb024-d533-43d6-af82-9b3fa089ac88" xlink:href="icui-20211231.xsd#icui_Hedge5Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_Hedge5Member_6dadb024-d533-43d6-af82-9b3fa089ac88" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_fb7442ec-6027-4f4b-91e2-4aeba977c950" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_us-gaap_InterestRateSwapMember_fb7442ec-6027-4f4b-91e2-4aeba977c950" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_UsGaap_InterestRateSwap2Member_0808407a-6d38-4f75-8ffa-5e8a426e4b7f" xlink:href="icui-20211231.xsd#icui_UsGaap_InterestRateSwap2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_d12f9fb6-b8e1-4b4c-9965-da9934a3e477" xlink:to="loc_icui_UsGaap_InterestRateSwap2Member_0808407a-6d38-4f75-8ffa-5e8a426e4b7f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_968c9780-80fd-45c7-b0e1-2891618dccce" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_8eed295c-b3c9-4e02-adcc-aebf81581e4f" xlink:to="loc_srt_RangeAxis_968c9780-80fd-45c7-b0e1-2891618dccce" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_968c9780-80fd-45c7-b0e1-2891618dccce_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_968c9780-80fd-45c7-b0e1-2891618dccce" xlink:to="loc_srt_RangeMember_968c9780-80fd-45c7-b0e1-2891618dccce_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_35183fec-42d6-42f2-b1d1-5357b6391909" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_968c9780-80fd-45c7-b0e1-2891618dccce" xlink:to="loc_srt_RangeMember_35183fec-42d6-42f2-b1d1-5357b6391909" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_b80f9768-9afc-4154-9e3a-1b8cd6e445d3" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_35183fec-42d6-42f2-b1d1-5357b6391909" xlink:to="loc_srt_MaximumMember_b80f9768-9afc-4154-9e3a-1b8cd6e445d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_61ea4afd-7410-4aa1-9147-a84189d6b01d" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_35183fec-42d6-42f2-b1d1-5357b6391909" xlink:to="loc_srt_MinimumMember_61ea4afd-7410-4aa1-9147-a84189d6b01d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativesandHedgingActivitiesDerivativeBalanceSheetLocationDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#DerivativesandHedgingActivitiesDerivativeBalanceSheetLocationDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativesandHedgingActivitiesDerivativeBalanceSheetLocationDetails" xlink:type="extended" id="i69aa797f4d844660ae11db2386bec5c6_DerivativesandHedgingActivitiesDerivativeBalanceSheetLocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_c0df4992-ba9a-4d3c-bc98-eb7a642b49a4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_f131a96f-076e-472d-b6d8-fb5853027647" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_c0df4992-ba9a-4d3c-bc98-eb7a642b49a4" xlink:to="loc_us-gaap_DerivativeAssets_f131a96f-076e-472d-b6d8-fb5853027647" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_8c17dc40-8a8e-4b31-8ea2-f767a4e8d9dd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_c0df4992-ba9a-4d3c-bc98-eb7a642b49a4" xlink:to="loc_us-gaap_DerivativeLiabilities_8c17dc40-8a8e-4b31-8ea2-f767a4e8d9dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_dc97b7d8-8588-4654-8448-608f23dbed45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_c0df4992-ba9a-4d3c-bc98-eb7a642b49a4" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_dc97b7d8-8588-4654-8448-608f23dbed45" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_3d651f73-e39c-4a8a-9aba-36edf78074b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_dc97b7d8-8588-4654-8448-608f23dbed45" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_3d651f73-e39c-4a8a-9aba-36edf78074b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3d651f73-e39c-4a8a-9aba-36edf78074b9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3d651f73-e39c-4a8a-9aba-36edf78074b9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3d651f73-e39c-4a8a-9aba-36edf78074b9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3d651f73-e39c-4a8a-9aba-36edf78074b9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_f0e5a28f-5b5c-419e-8d10-42dce2cbd354" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_f0e5a28f-5b5c-419e-8d10-42dce2cbd354" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_3df41b95-6780-4608-a636-f5dc0601fd8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:to="loc_us-gaap_InterestRateSwapMember_3df41b95-6780-4608-a636-f5dc0601fd8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_098cbd38-24d2-4991-bcd5-53dcb42e644d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_098cbd38-24d2-4991-bcd5-53dcb42e644d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_85619e68-7851-43c2-970a-015514bf8a26" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_85619e68-7851-43c2-970a-015514bf8a26" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsTotalMember_34a0e223-053e-4e1f-8173-26579517640f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_bd0ff965-50d6-4b4f-846e-527f2d0a0c42" xlink:to="loc_us-gaap_AssetsTotalMember_34a0e223-053e-4e1f-8173-26579517640f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_a0bdabcd-f27d-4046-8fd6-47f13ba36c40" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_dc97b7d8-8588-4654-8448-608f23dbed45" xlink:to="loc_us-gaap_HedgingDesignationAxis_a0bdabcd-f27d-4046-8fd6-47f13ba36c40" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a0bdabcd-f27d-4046-8fd6-47f13ba36c40_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_a0bdabcd-f27d-4046-8fd6-47f13ba36c40" xlink:to="loc_us-gaap_HedgingDesignationDomain_a0bdabcd-f27d-4046-8fd6-47f13ba36c40_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_a91b4b8a-da47-40bc-acef-53bc8ada6e53" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingDesignationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_a0bdabcd-f27d-4046-8fd6-47f13ba36c40" xlink:to="loc_us-gaap_HedgingDesignationDomain_a91b4b8a-da47-40bc-acef-53bc8ada6e53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_ba05110e-ae1c-4893-bc88-7718dd2e6a09" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DesignatedAsHedgingInstrumentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_a91b4b8a-da47-40bc-acef-53bc8ada6e53" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_ba05110e-ae1c-4893-bc88-7718dd2e6a09" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_d717c8a4-35e5-4927-aab6-95f9a11180cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_dc97b7d8-8588-4654-8448-608f23dbed45" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_d717c8a4-35e5-4927-aab6-95f9a11180cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_d717c8a4-35e5-4927-aab6-95f9a11180cd_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d717c8a4-35e5-4927-aab6-95f9a11180cd" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_d717c8a4-35e5-4927-aab6-95f9a11180cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_d717c8a4-35e5-4927-aab6-95f9a11180cd" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_177fff04-44e1-40fe-986b-d1412df081be" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_177fff04-44e1-40fe-986b-d1412df081be" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_ff0cf67c-d567-49e9-a549-a91b25942f62" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_ff0cf67c-d567-49e9-a549-a91b25942f62" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_efa80666-6b89-4cc5-a33c-d8dafd66bd81" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_OtherAssetsMember_efa80666-6b89-4cc5-a33c-d8dafd66bd81" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_998e1221-ddf8-4bc0-88fa-9b57b3d67664" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_998e1221-ddf8-4bc0-88fa-9b57b3d67664" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesMember_d31ef893-0d5d-47be-845d-24f8234a91d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_OtherLiabilitiesMember_d31ef893-0d5d-47be-845d-24f8234a91d3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsTotalMember_988d2ef0-6c47-43a6-9a67-9dc7016e4927" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_AssetsTotalMember_988d2ef0-6c47-43a6-9a67-9dc7016e4927" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_c779450f-ece6-463d-a6de-d36d9281cd93" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_c779450f-ece6-463d-a6de-d36d9281cd93" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesTotalMember_58816ae1-51bd-4f5e-934d-a377d3c0797b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_e0fc0518-bd2d-4e27-9bb2-198e66462592" xlink:to="loc_us-gaap_LiabilitiesTotalMember_58816ae1-51bd-4f5e-934d-a377d3c0797b" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativesandHedgingActivitiesDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#DerivativesandHedgingActivitiesDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativesandHedgingActivitiesDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended" id="i862f05c9924c47d4b15dc1c802fcc5c8_DerivativesandHedgingActivitiesDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_ba015430-9e89-4ef0-88f2-2f9a7fcc5d1d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_8e05069f-c9e2-4dc6-8636-69cb6235250d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_ba015430-9e89-4ef0-88f2-2f9a7fcc5d1d" xlink:to="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_8e05069f-c9e2-4dc6-8636-69cb6235250d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_e2ad9bcc-ac5d-4510-8e4e-0bf894a7543a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_ba015430-9e89-4ef0-88f2-2f9a7fcc5d1d" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_e2ad9bcc-ac5d-4510-8e4e-0bf894a7543a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_961aac4e-ef8e-4ac8-8c93-e605cba50a92" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_ba015430-9e89-4ef0-88f2-2f9a7fcc5d1d" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet_961aac4e-ef8e-4ac8-8c93-e605cba50a92" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_1be7d52b-c0ff-4419-a056-45bf66f8b9af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_ba015430-9e89-4ef0-88f2-2f9a7fcc5d1d" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_1be7d52b-c0ff-4419-a056-45bf66f8b9af" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_257e096e-2d1f-437f-a7b3-faab10a55ab7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_1be7d52b-c0ff-4419-a056-45bf66f8b9af" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_257e096e-2d1f-437f-a7b3-faab10a55ab7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_257e096e-2d1f-437f-a7b3-faab10a55ab7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_257e096e-2d1f-437f-a7b3-faab10a55ab7" xlink:to="loc_us-gaap_HedgingRelationshipDomain_257e096e-2d1f-437f-a7b3-faab10a55ab7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_aa8d7c8e-b43a-4c22-b0e9-4a06721ffabf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_257e096e-2d1f-437f-a7b3-faab10a55ab7" xlink:to="loc_us-gaap_HedgingRelationshipDomain_aa8d7c8e-b43a-4c22-b0e9-4a06721ffabf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_afaa4b91-05bd-4295-a880-878b72b80c43" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_aa8d7c8e-b43a-4c22-b0e9-4a06721ffabf" xlink:to="loc_us-gaap_CashFlowHedgingMember_afaa4b91-05bd-4295-a880-878b72b80c43" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_22ae3b36-c454-461a-b8d1-38c7e6194813" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_1be7d52b-c0ff-4419-a056-45bf66f8b9af" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_22ae3b36-c454-461a-b8d1-38c7e6194813" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_22ae3b36-c454-461a-b8d1-38c7e6194813_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_22ae3b36-c454-461a-b8d1-38c7e6194813" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_22ae3b36-c454-461a-b8d1-38c7e6194813_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_b8911d47-ae7d-486a-8e46-a8e25ac8b8b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_22ae3b36-c454-461a-b8d1-38c7e6194813" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_b8911d47-ae7d-486a-8e46-a8e25ac8b8b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_0dd7d788-d292-447d-b8a1-fbfdddb9a982" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_b8911d47-ae7d-486a-8e46-a8e25ac8b8b2" xlink:to="loc_us-gaap_CostOfSalesMember_0dd7d788-d292-447d-b8a1-fbfdddb9a982" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_f3d608d7-5177-4088-a0bc-4d9b8ec81803" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_1be7d52b-c0ff-4419-a056-45bf66f8b9af" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_f3d608d7-5177-4088-a0bc-4d9b8ec81803" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_f3d608d7-5177-4088-a0bc-4d9b8ec81803_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_f3d608d7-5177-4088-a0bc-4d9b8ec81803" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_f3d608d7-5177-4088-a0bc-4d9b8ec81803_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_e5ead52d-f434-43ce-aa02-e8a55f484597" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_f3d608d7-5177-4088-a0bc-4d9b8ec81803" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_e5ead52d-f434-43ce-aa02-e8a55f484597" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_310edbab-8453-46ca-a08e-1c04246af554" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeForwardMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e5ead52d-f434-43ce-aa02-e8a55f484597" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_310edbab-8453-46ca-a08e-1c04246af554" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_4ee30f43-4f9f-49e5-8dbe-167da8998e2c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e5ead52d-f434-43ce-aa02-e8a55f484597" xlink:to="loc_us-gaap_CashFlowHedgingMember_4ee30f43-4f9f-49e5-8dbe-167da8998e2c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_8a00c176-e131-490e-a6ef-96d45ca3bc6a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e5ead52d-f434-43ce-aa02-e8a55f484597" xlink:to="loc_us-gaap_InterestRateSwapMember_8a00c176-e131-490e-a6ef-96d45ca3bc6a" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementTables" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementTables"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementTables" xlink:type="extended" id="i1003c7210faf4e3cae334dd840d73fa3_FairValueMeasurementTables">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2b542fe5-c53c-42a8-89b8-c243d9baf3e1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTableTextBlock_0f907446-1896-4ec1-a029-24212ebdfa30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2b542fe5-c53c-42a8-89b8-c243d9baf3e1" xlink:to="loc_us-gaap_FairValueNetDerivativeAssetLiabilityMeasuredOnRecurringBasisUnobservableInputReconciliationTableTextBlock_0f907446-1896-4ec1-a029-24212ebdfa30" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_137f02ba-9508-480b-8d9c-4c69877b374b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2b542fe5-c53c-42a8-89b8-c243d9baf3e1" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_137f02ba-9508-480b-8d9c-4c69877b374b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_02068a98-8a65-465b-9e25-041f6feac522" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2b542fe5-c53c-42a8-89b8-c243d9baf3e1" xlink:to="loc_us-gaap_ScheduleOfFairValueAssetsAndLiabilitiesMeasuredOnRecurringBasisTableTextBlock_02068a98-8a65-465b-9e25-041f6feac522" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_959668a3-9357-416f-a414-65a24f7cdff0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2b542fe5-c53c-42a8-89b8-c243d9baf3e1" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_959668a3-9357-416f-a414-65a24f7cdff0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_96108439-4678-4993-93ea-87cacd7d449f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_959668a3-9357-416f-a414-65a24f7cdff0" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_96108439-4678-4993-93ea-87cacd7d449f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_96108439-4678-4993-93ea-87cacd7d449f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_96108439-4678-4993-93ea-87cacd7d449f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_96108439-4678-4993-93ea-87cacd7d449f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6b44f9b7-89e6-48cc-b40c-2e8ee3addd87" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_96108439-4678-4993-93ea-87cacd7d449f" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6b44f9b7-89e6-48cc-b40c-2e8ee3addd87" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_HospiraMember_c89046d9-ddf2-49ac-8d90-dc34523e439b" xlink:href="icui-20211231.xsd#icui_HospiraMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6b44f9b7-89e6-48cc-b40c-2e8ee3addd87" xlink:to="loc_icui_HospiraMember_c89046d9-ddf2-49ac-8d90-dc34523e439b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_da4c1cc7-2e86-4554-a974-fdfc7e2da134" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6b44f9b7-89e6-48cc-b40c-2e8ee3addd87" xlink:to="loc_icui_PursuitVascularInc.Member_da4c1cc7-2e86-4554-a974-fdfc7e2da134" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementTextDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementTextDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementTextDetails" xlink:type="extended" id="i522a46aec9ee4638ab58ae95a0e214a4_FairValueMeasurementTextDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_ceb2c863-5faf-4e1a-8e5d-83d00246ecbb" xlink:href="icui-20211231.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:to="loc_icui_Contingentconsiderationgross_ceb2c863-5faf-4e1a-8e5d-83d00246ecbb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_0e03f2fc-a632-4110-aa8f-1adecbd15da1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_0e03f2fc-a632-4110-aa8f-1adecbd15da1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermContingentConsiderationGross_c8932040-745a-42e3-a2f4-44f6a93c75a4" xlink:href="icui-20211231.xsd#icui_ShortTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:to="loc_icui_ShortTermContingentConsiderationGross_c8932040-745a-42e3-a2f4-44f6a93c75a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermContingentConsiderationGross_6f07b017-f60b-4547-8a18-3e77de7f482e" xlink:href="icui-20211231.xsd#icui_LongTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:to="loc_icui_LongTermContingentConsiderationGross_6f07b017-f60b-4547-8a18-3e77de7f482e" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_994d5384-d375-4798-9b5e-2978b47c39a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_8e30bbc5-98c7-43c4-80bd-dfcc58143911" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_994d5384-d375-4798-9b5e-2978b47c39a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_d986e72b-d458-4718-978d-56b610a2d050" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_994d5384-d375-4798-9b5e-2978b47c39a5" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_d986e72b-d458-4718-978d-56b610a2d050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d986e72b-d458-4718-978d-56b610a2d050_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d986e72b-d458-4718-978d-56b610a2d050" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d986e72b-d458-4718-978d-56b610a2d050_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d986e72b-d458-4718-978d-56b610a2d050" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_HospiraMember_5657ddb4-2667-4e04-907a-d61b531223c3" xlink:href="icui-20211231.xsd#icui_HospiraMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:to="loc_icui_HospiraMember_5657ddb4-2667-4e04-907a-d61b531223c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_4f2ddd2c-b05d-492d-9b82-c5d5f7edee1b" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:to="loc_icui_PursuitVascularInc.Member_4f2ddd2c-b05d-492d-9b82-c5d5f7edee1b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_0edaf43f-155b-44a8-b2f4-71726c5dae86" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:to="loc_icui_PursuitVascularLLCMember_0edaf43f-155b-44a8-b2f4-71726c5dae86" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignDistibutorMember_e737483e-c7a8-467d-8512-e35c0d584bcd" xlink:href="icui-20211231.xsd#icui_ForeignDistibutorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:to="loc_icui_ForeignDistibutorMember_e737483e-c7a8-467d-8512-e35c0d584bcd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_015d200d-5cbc-4c3c-84b3-fc425553775f" xlink:href="icui-20211231.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1c45506a-3816-4a14-92ad-1195684ea57d" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_015d200d-5cbc-4c3c-84b3-fc425553775f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementDetails" xlink:type="extended" id="i62fdab1f40b349b0bd6f9c6e6bfc7914_FairValueMeasurementDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_5ce31398-8062-4031-8945-a10825c60f78" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_5ce31398-8062-4031-8945-a10825c60f78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_f3101884-5633-49be-b6cf-892ed4997948" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationRecurringBasisLiabilityIssues_f3101884-5633-49be-b6cf-892ed4997948" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_21e349cc-924d-4d77-a663-6365af7d1590" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_21e349cc-924d-4d77-a663-6365af7d1590" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_7c5ca3d7-bca4-4a94-b57f-e259239199d1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationLiabilityTransfersOutOfLevel3_7c5ca3d7-bca4-4a94-b57f-e259239199d1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_b4b5130c-2302-41f6-baae-eabcf6ade32c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_6ac2bf80-5c53-4bf7-83b7-9b4ccdb9180a" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_b4b5130c-2302-41f6-baae-eabcf6ade32c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_3a5835af-7000-4a5d-b6f4-28983ec1f9bf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationTable_b4b5130c-2302-41f6-baae-eabcf6ade32c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_3a5835af-7000-4a5d-b6f4-28983ec1f9bf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3a5835af-7000-4a5d-b6f4-28983ec1f9bf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3a5835af-7000-4a5d-b6f4-28983ec1f9bf" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_3a5835af-7000-4a5d-b6f4-28983ec1f9bf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb117bb-7c74-4fab-aa09-fa2d43d7fe73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_3a5835af-7000-4a5d-b6f4-28983ec1f9bf" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb117bb-7c74-4fab-aa09-fa2d43d7fe73" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_e2a7060f-7cf8-4c95-8b32-8c5b08f9a621" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb117bb-7c74-4fab-aa09-fa2d43d7fe73" xlink:to="loc_icui_PursuitVascularInc.Member_e2a7060f-7cf8-4c95-8b32-8c5b08f9a621" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_HospiraMember_e5e9d91b-3d13-459a-992b-5d46ca7116d8" xlink:href="icui-20211231.xsd#icui_HospiraMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb117bb-7c74-4fab-aa09-fa2d43d7fe73" xlink:to="loc_icui_HospiraMember_e5e9d91b-3d13-459a-992b-5d46ca7116d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_448dc160-04cf-4403-9631-e9ada09712f9" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb117bb-7c74-4fab-aa09-fa2d43d7fe73" xlink:to="loc_icui_PursuitVascularLLCMember_448dc160-04cf-4403-9631-e9ada09712f9" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesHospiraQuantitativeInformationDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementFairValueInputsLiabilitiesHospiraQuantitativeInformationDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesHospiraQuantitativeInformationDetails" xlink:type="extended" id="i5e300d91c6fe4af7aa6b63d77313f904_FairValueMeasurementFairValueInputsLiabilitiesHospiraQuantitativeInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2935ac32-cdcc-4cc3-9b5a-e8f8505850c7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_6e0ad42c-eb26-47f8-8e23-5b7d7ef18658" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2935ac32-cdcc-4cc3-9b5a-e8f8505850c7" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_6e0ad42c-eb26-47f8-8e23-5b7d7ef18658" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_0c754a63-a655-454f-af4f-02ed58cbffd9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_2935ac32-cdcc-4cc3-9b5a-e8f8505850c7" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_0c754a63-a655-454f-af4f-02ed58cbffd9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_59d26c2a-ff80-414c-adae-086649e4acda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_0c754a63-a655-454f-af4f-02ed58cbffd9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_59d26c2a-ff80-414c-adae-086649e4acda" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59d26c2a-ff80-414c-adae-086649e4acda_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_59d26c2a-ff80-414c-adae-086649e4acda" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_59d26c2a-ff80-414c-adae-086649e4acda_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b2f926eb-1527-4dce-8588-9ac80f529901" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_59d26c2a-ff80-414c-adae-086649e4acda" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b2f926eb-1527-4dce-8588-9ac80f529901" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_HospiraMember_970df24d-0306-4333-83fc-a509af2ca86f" xlink:href="icui-20211231.xsd#icui_HospiraMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_b2f926eb-1527-4dce-8588-9ac80f529901" xlink:to="loc_icui_HospiraMember_970df24d-0306-4333-83fc-a509af2ca86f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_55fdf48b-845e-42d0-916a-6685ff116370" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_0c754a63-a655-454f-af4f-02ed58cbffd9" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_55fdf48b-845e-42d0-916a-6685ff116370" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_55fdf48b-845e-42d0-916a-6685ff116370_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_55fdf48b-845e-42d0-916a-6685ff116370" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_55fdf48b-845e-42d0-916a-6685ff116370_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_13b5fbbf-9a67-4fae-b3e4-713ce3e03307" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_55fdf48b-845e-42d0-916a-6685ff116370" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_13b5fbbf-9a67-4fae-b3e4-713ce3e03307" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_c9023fc5-5846-49f0-9955-67a6641e3e02" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_13b5fbbf-9a67-4fae-b3e4-713ce3e03307" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_c9023fc5-5846-49f0-9955-67a6641e3e02" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesPursuitQuantitativeInformationDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementFairValueInputsLiabilitiesPursuitQuantitativeInformationDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesPursuitQuantitativeInformationDetails" xlink:type="extended" id="i6497931180914bf2967f909e95775257_FairValueMeasurementFairValueInputsLiabilitiesPursuitQuantitativeInformationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_f560d621-8157-4656-802b-b7d5f2327554" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_a0ac10e8-8db8-436b-8c44-cfaf0f39993e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_f560d621-8157-4656-802b-b7d5f2327554" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_a0ac10e8-8db8-436b-8c44-cfaf0f39993e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fe464819-113d-45fc-b182-fb1a8e72dc9c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_f560d621-8157-4656-802b-b7d5f2327554" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fe464819-113d-45fc-b182-fb1a8e72dc9c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_45afda0e-f0ad-431e-83c4-00bd3ab9e031" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fe464819-113d-45fc-b182-fb1a8e72dc9c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_45afda0e-f0ad-431e-83c4-00bd3ab9e031" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45afda0e-f0ad-431e-83c4-00bd3ab9e031_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_45afda0e-f0ad-431e-83c4-00bd3ab9e031" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_45afda0e-f0ad-431e-83c4-00bd3ab9e031_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_456c33c6-c8d5-4e70-b5a8-c21daedc4290" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_45afda0e-f0ad-431e-83c4-00bd3ab9e031" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_456c33c6-c8d5-4e70-b5a8-c21daedc4290" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_2a2bf8a5-8c47-4b53-8c56-bae3df78ce8f" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_456c33c6-c8d5-4e70-b5a8-c21daedc4290" xlink:to="loc_icui_PursuitVascularInc.Member_2a2bf8a5-8c47-4b53-8c56-bae3df78ce8f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_16720be0-ab80-4547-8caf-87f777ea0d3c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_fe464819-113d-45fc-b182-fb1a8e72dc9c" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_16720be0-ab80-4547-8caf-87f777ea0d3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_16720be0-ab80-4547-8caf-87f777ea0d3c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_16720be0-ab80-4547-8caf-87f777ea0d3c" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_16720be0-ab80-4547-8caf-87f777ea0d3c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_16720be0-ab80-4547-8caf-87f777ea0d3c" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RevenueGrossProfitVolatilityMember_14f559e5-9d6a-4ad3-b98b-b120ab18c7e6" xlink:href="icui-20211231.xsd#icui_RevenueGrossProfitVolatilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:to="loc_icui_RevenueGrossProfitVolatilityMember_14f559e5-9d6a-4ad3-b98b-b120ab18c7e6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_ae94e771-bb13-408c-b5a2-8f9e67f50e06" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputDiscountRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_ae94e771-bb13-408c-b5a2-8f9e67f50e06" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_01257086-1623-451b-b429-26a531fa0269" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_01257086-1623-451b-b429-26a531fa0269" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditRiskMember_cc0ea43c-480d-45a7-9f7c-bbcdcea45d20" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditRiskMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_cf8126e0-6682-49bb-b905-b47a1927579c" xlink:to="loc_us-gaap_CreditRiskMember_cc0ea43c-480d-45a7-9f7c-bbcdcea45d20" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementsRecurringBasisDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#FairValueMeasurementFairValueMeasurementsRecurringBasisDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementsRecurringBasisDetails" xlink:type="extended" id="i8715f7e6067d4a9883a2a5f51c9af001_FairValueMeasurementFairValueMeasurementsRecurringBasisDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_440d5bed-2d2c-4536-a811-52e43aaa1f38" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_440d5bed-2d2c-4536-a811-52e43aaa1f38" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_3308f8ac-afbb-476d-aef3-f9734d4c09cf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_3308f8ac-afbb-476d-aef3-f9734d4c09cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_ced2c7cf-9433-495c-9b2b-1a589d651a7a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonfinancialLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_ced2c7cf-9433-495c-9b2b-1a589d651a7a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_c5423d64-2a8c-4c23-b9d8-d0ea2887d628" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_c5423d64-2a8c-4c23-b9d8-d0ea2887d628" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesNoncurrent_3b8c2520-20e4-48df-a0ef-258e9f52e522" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtSecuritiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_DebtSecuritiesNoncurrent_3b8c2520-20e4-48df-a0ef-258e9f52e522" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_d478cd7f-fe31-40b0-a1c8-db7b3f7e1c97" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateDerivativeLiabilitiesAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_d478cd7f-fe31-40b0-a1c8-db7b3f7e1c97" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c356bfbe-9638-4bf8-a267-e2ac61d62b8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7c60e730-b0a3-42b7-82bf-1a5c16a117b3" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c356bfbe-9638-4bf8-a267-e2ac61d62b8a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_8831b74b-6585-43bb-b305-a3e230025d8b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c356bfbe-9638-4bf8-a267-e2ac61d62b8a" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_8831b74b-6585-43bb-b305-a3e230025d8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8831b74b-6585-43bb-b305-a3e230025d8b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_8831b74b-6585-43bb-b305-a3e230025d8b" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8831b74b-6585-43bb-b305-a3e230025d8b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a02e9c02-d264-4062-ab94-e91a9a64b078" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_8831b74b-6585-43bb-b305-a3e230025d8b" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a02e9c02-d264-4062-ab94-e91a9a64b078" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EarnoutliabilityMember_a5b523d9-4b4c-4d2c-8acb-8332e958715b" xlink:href="icui-20211231.xsd#icui_EarnoutliabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a02e9c02-d264-4062-ab94-e91a9a64b078" xlink:to="loc_icui_EarnoutliabilityMember_a5b523d9-4b4c-4d2c-8acb-8332e958715b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesTotalMember_649abcfb-242f-45ab-93a5-cc3201eb0666" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_a02e9c02-d264-4062-ab94-e91a9a64b078" xlink:to="loc_us-gaap_LiabilitiesTotalMember_649abcfb-242f-45ab-93a5-cc3201eb0666" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_b941e21f-b340-4af0-a5c5-d68f80027237" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c356bfbe-9638-4bf8-a267-e2ac61d62b8a" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_b941e21f-b340-4af0-a5c5-d68f80027237" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_b941e21f-b340-4af0-a5c5-d68f80027237_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_b941e21f-b340-4af0-a5c5-d68f80027237" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_b941e21f-b340-4af0-a5c5-d68f80027237_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_0338e7d2-99aa-4efb-8e50-2336edf2904c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_b941e21f-b340-4af0-a5c5-d68f80027237" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_0338e7d2-99aa-4efb-8e50-2336edf2904c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_99f22829-7595-4f5d-8c17-cfd849794af6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_0338e7d2-99aa-4efb-8e50-2336edf2904c" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_99f22829-7595-4f5d-8c17-cfd849794af6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_91a47a0d-bbad-485c-828a-0f15c509329a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_c356bfbe-9638-4bf8-a267-e2ac61d62b8a" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_91a47a0d-bbad-485c-828a-0f15c509329a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_91a47a0d-bbad-485c-828a-0f15c509329a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_91a47a0d-bbad-485c-828a-0f15c509329a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_91a47a0d-bbad-485c-828a-0f15c509329a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d69c9cfa-13bd-4f56-be22-9d039cc07114" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_91a47a0d-bbad-485c-828a-0f15c509329a" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d69c9cfa-13bd-4f56-be22-9d039cc07114" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_360e56d5-33e1-421b-b135-55490e86063f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d69c9cfa-13bd-4f56-be22-9d039cc07114" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_360e56d5-33e1-421b-b135-55490e86063f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_d923f78e-b0cf-44fb-9347-e21cf92a94c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d69c9cfa-13bd-4f56-be22-9d039cc07114" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_d923f78e-b0cf-44fb-9347-e21cf92a94c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_0822122f-dd87-40d7-bf73-f84d9ac45a59" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_d69c9cfa-13bd-4f56-be22-9d039cc07114" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_0822122f-dd87-40d7-bf73-f84d9ac45a59" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#LongTermObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="extended" id="ifc1c35fb1bec4bb49fd917db591f42ca_LongTermObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_446acf90-e6f9-4fe9-9200-cab636150544" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_6d2656c7-b1b8-406d-be06-7b43616fc8df" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_446acf90-e6f9-4fe9-9200-cab636150544" xlink:to="loc_us-gaap_LongTermDebt_6d2656c7-b1b8-406d-be06-7b43616fc8df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_a428f719-ab33-49f2-bc6b-5de6bfa3beda" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_446acf90-e6f9-4fe9-9200-cab636150544" xlink:to="loc_us-gaap_DebtInstrumentTable_a428f719-ab33-49f2-bc6b-5de6bfa3beda" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_74291fa6-6106-432e-b13d-1379653b5cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a428f719-ab33-49f2-bc6b-5de6bfa3beda" xlink:to="loc_us-gaap_DebtInstrumentAxis_74291fa6-6106-432e-b13d-1379653b5cb8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_74291fa6-6106-432e-b13d-1379653b5cb8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_74291fa6-6106-432e-b13d-1379653b5cb8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_74291fa6-6106-432e-b13d-1379653b5cb8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_7d2da801-9023-44bc-8994-cd07c3cbad44" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_74291fa6-6106-432e-b13d-1379653b5cb8" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_7d2da801-9023-44bc-8994-cd07c3cbad44" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_06b2e41c-8345-4a9c-afef-0333f3bda914" xlink:href="icui-20211231.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7d2da801-9023-44bc-8994-cd07c3cbad44" xlink:to="loc_icui_TermLoanAMember_06b2e41c-8345-4a9c-afef-0333f3bda914" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_295054af-d674-46ac-bf7e-ed387bce57ef" xlink:href="icui-20211231.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7d2da801-9023-44bc-8994-cd07c3cbad44" xlink:to="loc_icui_TermLoanBMember_295054af-d674-46ac-bf7e-ed387bce57ef" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_8d19fa72-7960-4826-9f59-b4950fa94784" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_7d2da801-9023-44bc-8994-cd07c3cbad44" xlink:to="loc_us-gaap_LineOfCreditMember_8d19fa72-7960-4826-9f59-b4950fa94784" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_ae98648d-9e92-45eb-aa78-98d318b565a7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_a428f719-ab33-49f2-bc6b-5de6bfa3beda" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_ae98648d-9e92-45eb-aa78-98d318b565a7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_ae98648d-9e92-45eb-aa78-98d318b565a7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_ae98648d-9e92-45eb-aa78-98d318b565a7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_ae98648d-9e92-45eb-aa78-98d318b565a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_c30c280a-8dcb-48ce-99e1-fdc0ffa47925" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_ae98648d-9e92-45eb-aa78-98d318b565a7" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_c30c280a-8dcb-48ce-99e1-fdc0ffa47925" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_229326ce-19cd-4fb4-803a-c191e9202783" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_c30c280a-8dcb-48ce-99e1-fdc0ffa47925" xlink:to="loc_us-gaap_SubsequentEventMember_229326ce-19cd-4fb4-803a-c191e9202783" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsLineofCreditPricingDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#LongTermObligationsLineofCreditPricingDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsLineofCreditPricingDetails" xlink:type="extended" id="ie49727a781574a87959f6433a6f9b2fd_LongTermObligationsLineofCreditPricingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_d5fb409e-fb29-4f2b-ad24-65996c6d367a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_3edcfec4-7ea2-4a58-b9a1-f2e09c2ed852" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_d5fb409e-fb29-4f2b-ad24-65996c6d367a" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_3edcfec4-7ea2-4a58-b9a1-f2e09c2ed852" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LIBORBasisSpreadonVariableRate_1c5eca87-4f64-41cc-a43c-6d6145241b08" xlink:href="icui-20211231.xsd#icui_LIBORBasisSpreadonVariableRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_d5fb409e-fb29-4f2b-ad24-65996c6d367a" xlink:to="loc_icui_LIBORBasisSpreadonVariableRate_1c5eca87-4f64-41cc-a43c-6d6145241b08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4fca441f-9d71-4ac8-b4fc-d0d004b49f2a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_d5fb409e-fb29-4f2b-ad24-65996c6d367a" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_4fca441f-9d71-4ac8-b4fc-d0d004b49f2a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_8bc3b17c-6851-415c-b6f0-f364efab41a4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_d5fb409e-fb29-4f2b-ad24-65996c6d367a" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_8bc3b17c-6851-415c-b6f0-f364efab41a4" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_2766b3c9-7a2b-4cb1-b7fe-f2088049594c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_8bc3b17c-6851-415c-b6f0-f364efab41a4" xlink:to="loc_us-gaap_CreditFacilityAxis_2766b3c9-7a2b-4cb1-b7fe-f2088049594c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_2766b3c9-7a2b-4cb1-b7fe-f2088049594c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_2766b3c9-7a2b-4cb1-b7fe-f2088049594c" xlink:to="loc_us-gaap_CreditFacilityDomain_2766b3c9-7a2b-4cb1-b7fe-f2088049594c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_2766b3c9-7a2b-4cb1-b7fe-f2088049594c" xlink:to="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIMember_16d51bcb-dfff-4388-a7e2-c1e2290d361c" xlink:href="icui-20211231.xsd#icui_PricingLevelIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:to="loc_icui_PricingLevelIMember_16d51bcb-dfff-4388-a7e2-c1e2290d361c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIIMemberMember_a6fbdf90-b6b6-4b44-9696-81a39fcd9147" xlink:href="icui-20211231.xsd#icui_PricingLevelIIMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:to="loc_icui_PricingLevelIIMemberMember_a6fbdf90-b6b6-4b44-9696-81a39fcd9147" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIIIMemberMember_c26a24e4-e328-4a93-a16c-5ca32d3e0d4e" xlink:href="icui-20211231.xsd#icui_PricingLevelIIIMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:to="loc_icui_PricingLevelIIIMemberMember_c26a24e4-e328-4a93-a16c-5ca32d3e0d4e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIVMemberMember_07858faf-59c1-43c8-9710-e079c10c46d4" xlink:href="icui-20211231.xsd#icui_PricingLevelIVMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_b42be04c-079c-46bf-8b49-c75fcb3aef28" xlink:to="loc_icui_PricingLevelIVMemberMember_07858faf-59c1-43c8-9710-e079c10c46d4" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxesDeferredincometaxassetsliabilitiesDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#IncomeTaxesDeferredincometaxassetsliabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxesDeferredincometaxassetsliabilitiesDetails" xlink:type="extended" id="i89dc3a9d807b419cbc6e24f927bf3f47_IncomeTaxesDeferredincometaxassetsliabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:href="icui-20211231.xsd#icui_DeferredtaxassetsandliabilitiesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther_26c61cff-7ebc-4258-9eb8-831a1e7809b6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsOther_26c61cff-7ebc-4258-9eb8-831a1e7809b6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Noncurrentdeferredtaxassetacquiredfuturetaxdeductions_ef82d5bb-62df-4487-8f83-e8eee0ba942f" xlink:href="icui-20211231.xsd#icui_Noncurrentdeferredtaxassetacquiredfuturetaxdeductions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_Noncurrentdeferredtaxassetacquiredfuturetaxdeductions_ef82d5bb-62df-4487-8f83-e8eee0ba942f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_fb7bd65f-7fc7-4915-b208-b95535bf9809" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseCompensationAndBenefitsShareBasedCompensationCost_fb7bd65f-7fc7-4915-b208-b95535bf9809" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsUnrealizedCurrencyLosses_6d173e8e-9b25-4526-999d-268d7887db49" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsUnrealizedCurrencyLosses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsUnrealizedCurrencyLosses_6d173e8e-9b25-4526-999d-268d7887db49" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentDeferredTaxAssetTaxCreditsState_2b12d513-f70b-40a4-9649-7c8704f00627" xlink:href="icui-20211231.xsd#icui_NoncurrentDeferredTaxAssetTaxCreditsState"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_NoncurrentDeferredTaxAssetTaxCreditsState_2b12d513-f70b-40a4-9649-7c8704f00627" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsInventory_41a68afe-c256-412c-9233-f146326e77e9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsInventory_41a68afe-c256-412c-9233-f146326e77e9" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts_5a0b8922-1c82-4a0b-98fe-4a27626b66e0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsTaxDeferredExpenseReservesAndAccrualsAllowanceForDoubtfulAccounts_5a0b8922-1c82-4a0b-98fe-4a27626b66e0" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Noncurrentdeferredtaxassetaccruedrestructuring_59563d96-d734-4c7c-97ed-df9e8635c610" xlink:href="icui-20211231.xsd#icui_Noncurrentdeferredtaxassetaccruedrestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_Noncurrentdeferredtaxassetaccruedrestructuring_59563d96-d734-4c7c-97ed-df9e8635c610" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Noncurrentdeferredtaxassetchargebacksdiscountscustomerconcessions_c2fec132-abf9-4824-9acf-11b38356c1e9" xlink:href="icui-20211231.xsd#icui_Noncurrentdeferredtaxassetchargebacksdiscountscustomerconcessions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_Noncurrentdeferredtaxassetchargebacksdiscountscustomerconcessions_c2fec132-abf9-4824-9acf-11b38356c1e9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsValuationAllowance_c2685d35-4478-4c66-9418-4b51d770f434" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsValuationAllowance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsValuationAllowance_c2685d35-4478-4c66-9418-4b51d770f434" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Noncurrentdeferredtaxasset_c400b21c-1d25-4aec-ae43-422abeeeeb29" xlink:href="icui-20211231.xsd#icui_Noncurrentdeferredtaxasset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_Noncurrentdeferredtaxasset_c400b21c-1d25-4aec-ae43-422abeeeeb29" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentDeferredTaxLiabilityStateIncomeTaxes_59ddfe4c-f0f2-4228-9208-79611300e648" xlink:href="icui-20211231.xsd#icui_NoncurrentDeferredTaxLiabilityStateIncomeTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_NoncurrentDeferredTaxLiabilityStateIncomeTaxes_59ddfe4c-f0f2-4228-9208-79611300e648" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentDeferredTaxLiabilityForeign_b2a6147e-b173-429a-b573-80a84085ffe0" xlink:href="icui-20211231.xsd#icui_NoncurrentDeferredTaxLiabilityForeign"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_NoncurrentDeferredTaxLiabilityForeign_b2a6147e-b173-429a-b573-80a84085ffe0" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentDeferredTaxLiabilityDepreciationAndAmortization_98144daa-087b-447c-9b44-66877db27db7" xlink:href="icui-20211231.xsd#icui_NoncurrentDeferredTaxLiabilityDepreciationAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_NoncurrentDeferredTaxLiabilityDepreciationAndAmortization_98144daa-087b-447c-9b44-66877db27db7" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Deferredtaxliabilitychangeinaccountingmethod_c734edd6-5b2a-465e-ab17-20fb0dacccbc" xlink:href="icui-20211231.xsd#icui_Deferredtaxliabilitychangeinaccountingmethod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_Deferredtaxliabilitychangeinaccountingmethod_c734edd6-5b2a-465e-ab17-20fb0dacccbc" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxLiabilities_4529c9f2-ca0d-4d01-b8ef-223ca7b6269d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxLiabilities_4529c9f2-ca0d-4d01-b8ef-223ca7b6269d" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_44b63621-f600-48a2-a08d-baf2b74045cc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredTaxAssetsLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_us-gaap_DeferredTaxAssetsLiabilitiesNet_44b63621-f600-48a2-a08d-baf2b74045cc" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_DeferredtaxassetsandliabilitiesTable_fe05d425-8434-4b67-8252-49b2f386194b" xlink:href="icui-20211231.xsd#icui_DeferredtaxassetsandliabilitiesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesLineItems_24382016-91c8-4f16-946d-387d38c8e428" xlink:to="loc_icui_DeferredtaxassetsandliabilitiesTable_fe05d425-8434-4b67-8252-49b2f386194b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_c5b96e76-07ea-4cd1-bd95-93055cd07338" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_DeferredtaxassetsandliabilitiesTable_fe05d425-8434-4b67-8252-49b2f386194b" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_c5b96e76-07ea-4cd1-bd95-93055cd07338" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_c5b96e76-07ea-4cd1-bd95-93055cd07338_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_c5b96e76-07ea-4cd1-bd95-93055cd07338" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_c5b96e76-07ea-4cd1-bd95-93055cd07338_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_910068b6-a697-4244-a8e9-41859bb1f0aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_c5b96e76-07ea-4cd1-bd95-93055cd07338" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_910068b6-a697-4244-a8e9-41859bb1f0aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NonCurrentDeferredTaxAssetGrossTotalMember_dd47e525-e9df-43ef-b756-79dec6fe762c" xlink:href="icui-20211231.xsd#icui_NonCurrentDeferredTaxAssetGrossTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_910068b6-a697-4244-a8e9-41859bb1f0aa" xlink:to="loc_icui_NonCurrentDeferredTaxAssetGrossTotalMember_dd47e525-e9df-43ef-b756-79dec6fe762c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentDeferredTaxLiabilityMember_485c8b0b-791d-4f3b-913d-be092c930138" xlink:href="icui-20211231.xsd#icui_NoncurrentDeferredTaxLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_910068b6-a697-4244-a8e9-41859bb1f0aa" xlink:to="loc_icui_NoncurrentDeferredTaxLiabilityMember_485c8b0b-791d-4f3b-913d-be092c930138" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxesOperatingLossCarryforwardsDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#IncomeTaxesOperatingLossCarryforwardsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxesOperatingLossCarryforwardsDetails" xlink:type="extended" id="iafc636c5ffbf46baa83e8a0c14f3c288_IncomeTaxesOperatingLossCarryforwardsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsLineItems_508454ac-20eb-494e-8028-840fcd903466" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLossCarryforwardsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwards_741ac238-2242-47d1-aa5a-981f2556c7fe" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLossCarryforwards"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_508454ac-20eb-494e-8028-840fcd903466" xlink:to="loc_us-gaap_OperatingLossCarryforwards_741ac238-2242-47d1-aa5a-981f2556c7fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLossCarryforwardsTable_b54bc055-5d12-47c7-87a3-4fe5566681f1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLossCarryforwardsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLossCarryforwardsLineItems_508454ac-20eb-494e-8028-840fcd903466" xlink:to="loc_us-gaap_OperatingLossCarryforwardsTable_b54bc055-5d12-47c7-87a3-4fe5566681f1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_OperatingLossCarryforwardsTable_b54bc055-5d12-47c7-87a3-4fe5566681f1" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_fb34bfe6-af53-4c9d-bdd9-a82fa8f95401" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_96f7fa00-3763-4b1a-9f3f-0fe0ff057ddf" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_fb34bfe6-af53-4c9d-bdd9-a82fa8f95401" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_861bfab8-ac6e-47da-8d6c-926b5846bfe9" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_fb34bfe6-af53-4c9d-bdd9-a82fa8f95401" xlink:to="loc_country_US_861bfab8-ac6e-47da-8d6c-926b5846bfe9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StateAndLocalJurisdictionMember_40457ac2-8d7c-4403-b18e-00629c965a42" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StateAndLocalJurisdictionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_fb34bfe6-af53-4c9d-bdd9-a82fa8f95401" xlink:to="loc_us-gaap_StateAndLocalJurisdictionMember_40457ac2-8d7c-4403-b18e-00629c965a42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCountryMember_43902eee-3391-4407-987e-96d4ac61fd63" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCountryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxAuthorityDomain_fb34bfe6-af53-4c9d-bdd9-a82fa8f95401" xlink:to="loc_us-gaap_ForeignCountryMember_43902eee-3391-4407-987e-96d4ac61fd63" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxesTaxHolidayDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#IncomeTaxesTaxHolidayDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxesTaxHolidayDetails" xlink:type="extended" id="ifeb98386b88c4e66964a5df2deb7f732_IncomeTaxesTaxHolidayDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxHolidayLineItems_34227461-0078-4717-99a1-948c4e315fce" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxHolidayLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxHolidayAggregateDollarAmount_8ef14d08-0272-4a53-a765-d892e1296b3f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxHolidayAggregateDollarAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxHolidayLineItems_34227461-0078-4717-99a1-948c4e315fce" xlink:to="loc_us-gaap_IncomeTaxHolidayAggregateDollarAmount_8ef14d08-0272-4a53-a765-d892e1296b3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare_c86f0791-0bc1-4c27-a783-5fe3ff60470b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeTaxHolidayLineItems_34227461-0078-4717-99a1-948c4e315fce" xlink:to="loc_us-gaap_IncomeTaxHolidayIncomeTaxBenefitsPerShare_c86f0791-0bc1-4c27-a783-5fe3ff60470b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxHolidayTable_a279f898-6d82-4264-8207-61ebf7322f73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxHolidayTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeTaxHolidayLineItems_34227461-0078-4717-99a1-948c4e315fce" xlink:to="loc_us-gaap_IncomeTaxHolidayTable_a279f898-6d82-4264-8207-61ebf7322f73" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityAxis_951b7387-5910-40a9-97b6-b782cc3603ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeTaxHolidayTable_a279f898-6d82-4264-8207-61ebf7322f73" xlink:to="loc_us-gaap_IncomeTaxAuthorityAxis_951b7387-5910-40a9-97b6-b782cc3603ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_951b7387-5910-40a9-97b6-b782cc3603ac_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_951b7387-5910-40a9-97b6-b782cc3603ac" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_951b7387-5910-40a9-97b6-b782cc3603ac_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxAuthorityDomain_79ed2118-f82d-46dd-9aa3-682629e36b3d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeTaxAuthorityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeTaxAuthorityAxis_951b7387-5910-40a9-97b6-b782cc3603ac" xlink:to="loc_us-gaap_IncomeTaxAuthorityDomain_79ed2118-f82d-46dd-9aa3-682629e36b3d" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GeographicInformationandSignificantCustomersLongLivedAssetsbyGeographicLocationDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#GeographicInformationandSignificantCustomersLongLivedAssetsbyGeographicLocationDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GeographicInformationandSignificantCustomersLongLivedAssetsbyGeographicLocationDetails" xlink:type="extended" id="i4066237eeb7641228d52fdcaad23cba8_GeographicInformationandSignificantCustomersLongLivedAssetsbyGeographicLocationDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_ad567993-7e2e-4593-ab62-e62a9577576b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncurrentAssets_39880e11-059b-4ef8-9c36-ecaee53830ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_ad567993-7e2e-4593-ab62-e62a9577576b" xlink:to="loc_us-gaap_NoncurrentAssets_39880e11-059b-4ef8-9c36-ecaee53830ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8520bc45-0d40-4075-a780-c41c6c281d9e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_ad567993-7e2e-4593-ab62-e62a9577576b" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8520bc45-0d40-4075-a780-c41c6c281d9e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_1f032593-f14a-41c5-900c-95c5ba944631" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_8520bc45-0d40-4075-a780-c41c6c281d9e" xlink:to="loc_srt_StatementGeographicalAxis_1f032593-f14a-41c5-900c-95c5ba944631" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_1f032593-f14a-41c5-900c-95c5ba944631_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_1f032593-f14a-41c5-900c-95c5ba944631" xlink:to="loc_srt_SegmentGeographicalDomain_1f032593-f14a-41c5-900c-95c5ba944631_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_1f032593-f14a-41c5-900c-95c5ba944631" xlink:to="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CR_9dae563d-3da8-4d15-a54b-382583bc288a" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_CR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_country_CR_9dae563d-3da8-4d15-a54b-382583bc288a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MexicoPropertyAndEquipmentMember_c45a73a3-b1ff-4c9a-9916-dba12234b260" xlink:href="icui-20211231.xsd#icui_MexicoPropertyAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_icui_MexicoPropertyAndEquipmentMember_c45a73a3-b1ff-4c9a-9916-dba12234b260" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherLATAMMember_bce45535-d18f-4f34-b505-76e67fcfeab8" xlink:href="icui-20211231.xsd#icui_OtherLATAMMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_icui_OtherLATAMMember_bce45535-d18f-4f34-b505-76e67fcfeab8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_9b0a0411-f0db-44be-a8f0-0942cfc931c3" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_country_CA_9b0a0411-f0db-44be-a8f0-0942cfc931c3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ItalyPropertyAndEquipmentMember_29ec74b0-d80b-42f6-9f81-dda47accb481" xlink:href="icui-20211231.xsd#icui_ItalyPropertyAndEquipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_icui_ItalyPropertyAndEquipmentMember_29ec74b0-d80b-42f6-9f81-dda47accb481" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_ES_a13a2bb9-a814-4c9e-b8a0-701d629ced1d" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_ES"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_country_ES_a13a2bb9-a814-4c9e-b8a0-701d629ced1d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_085d8dfc-6d0c-47ac-8908-beac551ccf8b" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_srt_EuropeMember_085d8dfc-6d0c-47ac-8908-beac551ccf8b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_5087dcc0-c85c-4f09-81d7-3c9bc0966b69" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_srt_AsiaPacificMember_5087dcc0-c85c-4f09-81d7-3c9bc0966b69" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignMember_828f3e03-5bea-4455-95ac-2fed7b04530d" xlink:href="icui-20211231.xsd#icui_ForeignMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_icui_ForeignMember_828f3e03-5bea-4455-95ac-2fed7b04530d" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_UnitedStatespropertyandequipmentMember_fad2a4b8-1d78-41dc-8506-2bb00e6df992" xlink:href="icui-20211231.xsd#icui_UnitedStatespropertyandequipmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_cf0b3fd3-ccda-44f6-9453-e147b74262d6" xlink:to="loc_icui_UnitedStatespropertyandequipmentMember_fad2a4b8-1d78-41dc-8506-2bb00e6df992" xlink:type="arc" order="9"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#StockholdersEquityDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityDetails" xlink:type="extended" id="i624047ab8410478bbbd236106bac2919_StockholdersEquityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityClassOfTreasuryStockLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_3ddbbd12-e32e-4dfd-ac85-b5a1b28f28c4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_3ddbbd12-e32e-4dfd-ac85-b5a1b28f28c4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_e6215a1b-b4db-4b6f-90d7-047e115fe8af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_e6215a1b-b4db-4b6f-90d7-047e115fe8af" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_7c1496c8-5912-49ae-9e72-4156cf251c03" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_7c1496c8-5912-49ae-9e72-4156cf251c03" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_794d82fa-b493-4390-9a06-b3ee3cb5eb05" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_794d82fa-b493-4390-9a06-b3ee3cb5eb05" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonShares_725013eb-8e93-4fbe-b1e3-46e3ebfdda5a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TreasuryStockCommonShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_TreasuryStockCommonShares_725013eb-8e93-4fbe-b1e3-46e3ebfdda5a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ClassOfTreasuryStockTable_5e840027-cab8-41f2-9caf-094ff93ccbf3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfTreasuryStockTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquityClassOfTreasuryStockLineItems_24cdb581-0f55-4531-9f55-cc41c75f3a17" xlink:to="loc_us-gaap_ClassOfTreasuryStockTable_5e840027-cab8-41f2-9caf-094ff93ccbf3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_9cff217e-abf0-47ca-a9db-2eb862a6cec0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ClassOfTreasuryStockTable_5e840027-cab8-41f2-9caf-094ff93ccbf3" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_9cff217e-abf0-47ca-a9db-2eb862a6cec0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_9cff217e-abf0-47ca-a9db-2eb862a6cec0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9cff217e-abf0-47ca-a9db-2eb862a6cec0" xlink:to="loc_us-gaap_EquityComponentDomain_9cff217e-abf0-47ca-a9db-2eb862a6cec0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_879ab89c-b2f7-409f-af51-4cb797796cdd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_9cff217e-abf0-47ca-a9db-2eb862a6cec0" xlink:to="loc_us-gaap_EquityComponentDomain_879ab89c-b2f7-409f-af51-4cb797796cdd" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#StockholdersEquityAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended" id="i6ea553859bec4766a62d297f17af76f3_StockholdersEquityAccumulatedOtherComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_efc5249e-cb0f-44bd-89a8-351b94c39915" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_efc5249e-cb0f-44bd-89a8-351b94c39915" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_ab4ce26c-8050-41ad-bc26-92310004174c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_ab4ce26c-8050-41ad-bc26-92310004174c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_5663e0e4-8712-4a7c-b9aa-30da3bd7d0ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_5663e0e4-8712-4a7c-b9aa-30da3bd7d0ee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_a61fff28-4829-480e-ad16-bebad1179e1d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_a61fff28-4829-480e-ad16-bebad1179e1d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_e8383c2f-d4f2-405d-af09-d0f08350d908" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_4e8eead3-e2d2-4e9c-9401-6910bf360a63" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_e8383c2f-d4f2-405d-af09-d0f08350d908" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_73cf4de6-c901-42ff-8a11-f497fd10cd51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_e8383c2f-d4f2-405d-af09-d0f08350d908" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_73cf4de6-c901-42ff-8a11-f497fd10cd51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_73cf4de6-c901-42ff-8a11-f497fd10cd51_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_73cf4de6-c901-42ff-8a11-f497fd10cd51" xlink:to="loc_us-gaap_EquityComponentDomain_73cf4de6-c901-42ff-8a11-f497fd10cd51_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_34c01fcb-5cfe-4b53-8cbd-9049d11aac1c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_73cf4de6-c901-42ff-8a11-f497fd10cd51" xlink:to="loc_us-gaap_EquityComponentDomain_34c01fcb-5cfe-4b53-8cbd-9049d11aac1c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_9ba0d6d7-b026-4f05-9e05-0d6fb17f30b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_34c01fcb-5cfe-4b53-8cbd-9049d11aac1c" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_9ba0d6d7-b026-4f05-9e05-0d6fb17f30b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_741f4381-ab76-4883-b8b1-451d673bf2a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_34c01fcb-5cfe-4b53-8cbd-9049d11aac1c" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_741f4381-ab76-4883-b8b1-451d673bf2a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_3752b0ba-094b-4e91-bf20-6bf6ec1ba4f1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_34c01fcb-5cfe-4b53-8cbd-9049d11aac1c" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_3752b0ba-094b-4e91-bf20-6bf6ec1ba4f1" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CommitmentsandContingenciesContingenciesDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#CommitmentsandContingenciesContingenciesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CommitmentsandContingenciesContingenciesDetails" xlink:type="extended" id="i2924a94f2fab4627b16930798cf32d73_CommitmentsandContingenciesContingenciesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_be5774a7-86cb-4aea-a586-cda4d845e635" xlink:href="icui-20211231.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:to="loc_icui_Contingentconsiderationgross_be5774a7-86cb-4aea-a586-cda4d845e635" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_b8c23235-657e-4805-b56d-98946f8369a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_b8c23235-657e-4805-b56d-98946f8369a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermContingentConsiderationGross_c7c31fed-4671-4828-8a6a-4b93d9d2a81a" xlink:href="icui-20211231.xsd#icui_ShortTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:to="loc_icui_ShortTermContingentConsiderationGross_c7c31fed-4671-4828-8a6a-4b93d9d2a81a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermContingentConsiderationGross_4ae23257-6f88-4b38-9933-c391e5d9d602" xlink:href="icui-20211231.xsd#icui_LongTermContingentConsiderationGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:to="loc_icui_LongTermContingentConsiderationGross_4ae23257-6f88-4b38-9933-c391e5d9d602" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d74e37f0-21fe-400e-bcb2-4629867f4b36" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_fc2e00de-94fa-4137-bd2f-5c97c55400ee" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d74e37f0-21fe-400e-bcb2-4629867f4b36" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_c4643712-cd03-4a96-be9e-7b0e62269007" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d74e37f0-21fe-400e-bcb2-4629867f4b36" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_c4643712-cd03-4a96-be9e-7b0e62269007" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c4643712-cd03-4a96-be9e-7b0e62269007_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c4643712-cd03-4a96-be9e-7b0e62269007" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c4643712-cd03-4a96-be9e-7b0e62269007_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_c4643712-cd03-4a96-be9e-7b0e62269007" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_HospiraMember_b1f87c13-78ed-40d7-9c1c-aa04ba61d387" xlink:href="icui-20211231.xsd#icui_HospiraMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:to="loc_icui_HospiraMember_b1f87c13-78ed-40d7-9c1c-aa04ba61d387" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_afdd86d0-7aa3-4edc-a828-4cfbc7972566" xlink:href="icui-20211231.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:to="loc_icui_PursuitVascularInc.Member_afdd86d0-7aa3-4edc-a828-4cfbc7972566" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularLLCMember_f2a4e692-405e-428f-a31a-93c0c1c23424" xlink:href="icui-20211231.xsd#icui_PursuitVascularLLCMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:to="loc_icui_PursuitVascularLLCMember_f2a4e692-405e-428f-a31a-93c0c1c23424" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignDistibutorMember_199e429b-6f94-4cc6-b8f6-c65b8e067891" xlink:href="icui-20211231.xsd#icui_ForeignDistibutorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:to="loc_icui_ForeignDistibutorMember_199e429b-6f94-4cc6-b8f6-c65b8e067891" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_7f5fa587-1e1d-4d18-91f4-2d1685f3a290" xlink:href="icui-20211231.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f6632443-0273-49b4-963e-5f9440a888ec" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_7f5fa587-1e1d-4d18-91f4-2d1685f3a290" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_5432938f-4b6c-408a-81e5-f161adfd2448" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_d74e37f0-21fe-400e-bcb2-4629867f4b36" xlink:to="loc_srt_RangeAxis_5432938f-4b6c-408a-81e5-f161adfd2448" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_5432938f-4b6c-408a-81e5-f161adfd2448_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_5432938f-4b6c-408a-81e5-f161adfd2448" xlink:to="loc_srt_RangeMember_5432938f-4b6c-408a-81e5-f161adfd2448_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c9e5a6f9-fa93-4f41-9fa6-f1f2599f36b2" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_5432938f-4b6c-408a-81e5-f161adfd2448" xlink:to="loc_srt_RangeMember_c9e5a6f9-fa93-4f41-9fa6-f1f2599f36b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_bba7437d-b9c7-4dd3-aaa4-160f706277d7" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c9e5a6f9-fa93-4f41-9fa6-f1f2599f36b2" xlink:to="loc_srt_MinimumMember_bba7437d-b9c7-4dd3-aaa4-160f706277d7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ac3d0b4d-c197-4831-b917-46de8424e1da" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c9e5a6f9-fa93-4f41-9fa6-f1f2599f36b2" xlink:to="loc_srt_MaximumMember_ac3d0b4d-c197-4831-b917-46de8424e1da" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsDetails" xlink:type="extended" id="i5ce132161deb4faf8c31e5028464456b_SubsequentEventsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_6a8235c3-8568-42a6-a3a1-a2c985e47597" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_6a8235c3-8568-42a6-a3a1-a2c985e47597" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesGross_609c0583-7d7c-4655-b752-1333ee29af30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_609c0583-7d7c-4655-b752-1333ee29af30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_f335a211-87ab-452e-b480-8ead9d0e6322" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_f335a211-87ab-452e-b480-8ead9d0e6322" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_fe1dc53f-ed36-42a2-8c15-6a9bfa80f770" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_us-gaap_CommonStockValue_fe1dc53f-ed36-42a2-8c15-6a9bfa80f770" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_dbb285b1-87ad-47b8-8f9c-e4437aca5731" xlink:href="icui-20211231.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_icui_Contingentconsiderationgross_dbb285b1-87ad-47b8-8f9c-e4437aca5731" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OwnershipShareMinimumRequirement_aa5ab0f3-9257-418a-b887-7c4b3536fe40" xlink:href="icui-20211231.xsd#icui_OwnershipShareMinimumRequirement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_icui_OwnershipShareMinimumRequirement_aa5ab0f3-9257-418a-b887-7c4b3536fe40" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_8b79f191-d923-4db8-9044-7a215b07f5a5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_e5900682-975d-401a-9552-0b3965cca1f9" xlink:to="loc_us-gaap_SubsequentEventTable_8b79f191-d923-4db8-9044-7a215b07f5a5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_3229d181-2c02-4ac1-82e4-cf96b26e2f2b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8b79f191-d923-4db8-9044-7a215b07f5a5" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_3229d181-2c02-4ac1-82e4-cf96b26e2f2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3229d181-2c02-4ac1-82e4-cf96b26e2f2b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3229d181-2c02-4ac1-82e4-cf96b26e2f2b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3229d181-2c02-4ac1-82e4-cf96b26e2f2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_07fe0a59-e245-4c90-99b0-79128a948c69" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_3229d181-2c02-4ac1-82e4-cf96b26e2f2b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_07fe0a59-e245-4c90-99b0-79128a948c69" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_135bc26f-f9c0-4553-8e40-c9b7ddefe2d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_07fe0a59-e245-4c90-99b0-79128a948c69" xlink:to="loc_us-gaap_SubsequentEventMember_135bc26f-f9c0-4553-8e40-c9b7ddefe2d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_4d01f249-17b7-44d9-8dcd-8b1ec82760c2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_8b79f191-d923-4db8-9044-7a215b07f5a5" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_4d01f249-17b7-44d9-8dcd-8b1ec82760c2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4d01f249-17b7-44d9-8dcd-8b1ec82760c2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4d01f249-17b7-44d9-8dcd-8b1ec82760c2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_4d01f249-17b7-44d9-8dcd-8b1ec82760c2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6db065dd-e4a0-48d8-b011-7e742cd47960" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_4d01f249-17b7-44d9-8dcd-8b1ec82760c2" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6db065dd-e4a0-48d8-b011-7e742cd47960" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_fcf51fbb-3153-478e-908a-360331becd5a" xlink:href="icui-20211231.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6db065dd-e4a0-48d8-b011-7e742cd47960" xlink:to="loc_icui_SmithsMedicalMember_fcf51fbb-3153-478e-908a-360331becd5a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsCreditAgreementDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#SubsequentEventsCreditAgreementDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsCreditAgreementDetails" xlink:type="extended" id="i60fe110db8c6435b90aa7ed4f75e915b_SubsequentEventsCreditAgreementDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_54a2cb65-99a9-41c9-bd5b-129885c36300" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_us-gaap_LongTermDebt_54a2cb65-99a9-41c9-bd5b-129885c36300" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAPaymentFirstYearsAsAOfOriginalDebt_31f905c9-f6c8-4e04-91ca-c34ef906fbeb" xlink:href="icui-20211231.xsd#icui_TermLoanAPaymentFirstYearsAsAOfOriginalDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanAPaymentFirstYearsAsAOfOriginalDebt_31f905c9-f6c8-4e04-91ca-c34ef906fbeb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAPaymentYear3And4AsAOfOriginalDebtAmount_f1e7d07f-9db7-4ed0-b902-f047cbc8be34" xlink:href="icui-20211231.xsd#icui_TermLoanAPaymentYear3And4AsAOfOriginalDebtAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanAPaymentYear3And4AsAOfOriginalDebtAmount_f1e7d07f-9db7-4ed0-b902-f047cbc8be34" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAPaymentYear5_6721ed40-fff0-4097-934e-0ff4a933a186" xlink:href="icui-20211231.xsd#icui_TermLoanAPaymentYear5"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanAPaymentYear5_6721ed40-fff0-4097-934e-0ff4a933a186" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBQuarterlyPaymentsAsAOfOriginalDebtAmount_7b870b0b-cbda-4f51-ac67-b971fab4ffe6" xlink:href="icui-20211231.xsd#icui_TermLoanBQuarterlyPaymentsAsAOfOriginalDebtAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanBQuarterlyPaymentsAsAOfOriginalDebtAmount_7b870b0b-cbda-4f51-ac67-b971fab4ffe6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LineOfCreditSpread_5e9d1766-b533-4b3e-9892-b2f75f1a9aa7" xlink:href="icui-20211231.xsd#icui_LineOfCreditSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_LineOfCreditSpread_5e9d1766-b533-4b3e-9892-b2f75f1a9aa7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAAndCreditLineSpread_6a5aa4e1-835d-456c-9fa3-9f5ac5a46b96" xlink:href="icui-20211231.xsd#icui_TermLoanAAndCreditLineSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanAAndCreditLineSpread_6a5aa4e1-835d-456c-9fa3-9f5ac5a46b96" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBInitialSpread_1e30c274-413c-41f8-96e8-bc7adc521a17" xlink:href="icui-20211231.xsd#icui_TermLoanBInitialSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_icui_TermLoanBInitialSpread_1e30c274-413c-41f8-96e8-bc7adc521a17" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_e3274774-ac8f-4660-9f53-9ca2ce2b038a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_8809571c-7c14-492a-b1a3-b09f85a2be73" xlink:to="loc_us-gaap_SubsequentEventTable_e3274774-ac8f-4660-9f53-9ca2ce2b038a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_b26fb542-64eb-40d1-ab12-b94cd4c5417c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_e3274774-ac8f-4660-9f53-9ca2ce2b038a" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_b26fb542-64eb-40d1-ab12-b94cd4c5417c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_b26fb542-64eb-40d1-ab12-b94cd4c5417c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_b26fb542-64eb-40d1-ab12-b94cd4c5417c" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_b26fb542-64eb-40d1-ab12-b94cd4c5417c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9d5b4a97-40f9-4ef9-85c4-501b041a0b51" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_b26fb542-64eb-40d1-ab12-b94cd4c5417c" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9d5b4a97-40f9-4ef9-85c4-501b041a0b51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_59aad036-7c87-44cf-a253-c5ca45daeff5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_9d5b4a97-40f9-4ef9-85c4-501b041a0b51" xlink:to="loc_us-gaap_SubsequentEventMember_59aad036-7c87-44cf-a253-c5ca45daeff5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_95d96d6e-3904-4313-b074-365e6d9aa0e2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_e3274774-ac8f-4660-9f53-9ca2ce2b038a" xlink:to="loc_us-gaap_DebtInstrumentAxis_95d96d6e-3904-4313-b074-365e6d9aa0e2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_95d96d6e-3904-4313-b074-365e6d9aa0e2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_95d96d6e-3904-4313-b074-365e6d9aa0e2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_95d96d6e-3904-4313-b074-365e6d9aa0e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_95d96d6e-3904-4313-b074-365e6d9aa0e2" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoansLineOfCreditMember_86118222-7f74-4f9b-a479-8dcde1d3ee63" xlink:href="icui-20211231.xsd#icui_TermLoansLineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:to="loc_icui_TermLoansLineOfCreditMember_86118222-7f74-4f9b-a479-8dcde1d3ee63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_0c640a14-b68a-4b76-8beb-7a99f1852761" xlink:href="icui-20211231.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:to="loc_icui_TermLoanAMember_0c640a14-b68a-4b76-8beb-7a99f1852761" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_73ca755e-202f-4bd1-a0e1-2798f13b8366" xlink:href="icui-20211231.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:to="loc_icui_TermLoanBMember_73ca755e-202f-4bd1-a0e1-2798f13b8366" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_c2b78cf2-6131-4595-9647-17cfea971ac5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_fec06b46-c0d1-4e03-a940-5d9d0ed36e8a" xlink:to="loc_us-gaap_LineOfCreditMember_c2b78cf2-6131-4595-9647-17cfea971ac5" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsTermLoanACreditLineApplicableMarginDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#SubsequentEventsTermLoanACreditLineApplicableMarginDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsTermLoanACreditLineApplicableMarginDetails" xlink:type="extended" id="ieabcde2275fd41dd8e1875cccca0df65_SubsequentEventsTermLoanACreditLineApplicableMarginDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Spread_3a7c3ad5-d82e-4075-8351-72040f4f1523" xlink:href="icui-20211231.xsd#icui_Spread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:to="loc_icui_Spread_3a7c3ad5-d82e-4075-8351-72040f4f1523" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_9fe75d5d-eb53-48bf-ac50-82e3f04c8df7" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentBasisSpreadOnVariableRate1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:to="loc_us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_9fe75d5d-eb53-48bf-ac50-82e3f04c8df7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_7154dd13-0fd3-48ad-87dc-6b22bb4e582f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_7154dd13-0fd3-48ad-87dc-6b22bb4e582f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAAndCreditLineSpread_fb671e45-026b-43e5-a4a6-91db15d3ead9" xlink:href="icui-20211231.xsd#icui_TermLoanAAndCreditLineSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:to="loc_icui_TermLoanAAndCreditLineSpread_fb671e45-026b-43e5-a4a6-91db15d3ead9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_24bea94c-de28-41a9-a68a-407f950e86ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_3cddb6f4-2ed5-494d-8841-ae8ff0027aa6" xlink:to="loc_us-gaap_SubsequentEventTable_24bea94c-de28-41a9-a68a-407f950e86ac" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_9241b820-9925-4614-adc9-a032594e05d8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_24bea94c-de28-41a9-a68a-407f950e86ac" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_9241b820-9925-4614-adc9-a032594e05d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_9241b820-9925-4614-adc9-a032594e05d8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_9241b820-9925-4614-adc9-a032594e05d8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_9241b820-9925-4614-adc9-a032594e05d8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_c6c3f33f-064d-430c-8a63-b6fb29267c9f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_9241b820-9925-4614-adc9-a032594e05d8" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_c6c3f33f-064d-430c-8a63-b6fb29267c9f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_70445149-b5c0-471a-a94d-4bf4810f7f45" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_c6c3f33f-064d-430c-8a63-b6fb29267c9f" xlink:to="loc_us-gaap_SubsequentEventMember_70445149-b5c0-471a-a94d-4bf4810f7f45" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadAxis_1b97ffc0-5489-43a1-9f70-c6873de29ac0" xlink:href="icui-20211231.xsd#icui_TermLoanAAndCreditLineApplicableMarginSpreadAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_24bea94c-de28-41a9-a68a-407f950e86ac" xlink:to="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadAxis_1b97ffc0-5489-43a1-9f70-c6873de29ac0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_1b97ffc0-5489-43a1-9f70-c6873de29ac0_default" xlink:href="icui-20211231.xsd#icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadAxis_1b97ffc0-5489-43a1-9f70-c6873de29ac0" xlink:to="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_1b97ffc0-5489-43a1-9f70-c6873de29ac0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:href="icui-20211231.xsd#icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadAxis_1b97ffc0-5489-43a1-9f70-c6873de29ac0" xlink:to="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevel5Member_5e109094-32a0-40ba-9d1d-50a77edc26ac" xlink:href="icui-20211231.xsd#icui_PricingLevel5Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:to="loc_icui_PricingLevel5Member_5e109094-32a0-40ba-9d1d-50a77edc26ac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIVMemberMember_71c73642-996f-4b4f-ab16-335f0b2f4983" xlink:href="icui-20211231.xsd#icui_PricingLevelIVMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:to="loc_icui_PricingLevelIVMemberMember_71c73642-996f-4b4f-ab16-335f0b2f4983" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIIIMemberMember_0b682553-886a-4472-b69a-4514b1db63f1" xlink:href="icui-20211231.xsd#icui_PricingLevelIIIMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:to="loc_icui_PricingLevelIIIMemberMember_0b682553-886a-4472-b69a-4514b1db63f1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIIMemberMember_a05ccb16-123e-4ad1-af67-5d9cc715b3f9" xlink:href="icui-20211231.xsd#icui_PricingLevelIIMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:to="loc_icui_PricingLevelIIMemberMember_a05ccb16-123e-4ad1-af67-5d9cc715b3f9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIMember_8becc828-bb4c-4dc2-9c29-baf2cf7d3e41" xlink:href="icui-20211231.xsd#icui_PricingLevelIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanAAndCreditLineApplicableMarginSpreadDomain_8b47605c-1564-428a-a372-b8fe2a850530" xlink:to="loc_icui_PricingLevelIMember_8becc828-bb4c-4dc2-9c29-baf2cf7d3e41" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsTermLoanBApplicableMarginDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#SubsequentEventsTermLoanBApplicableMarginDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsTermLoanBApplicableMarginDetails" xlink:type="extended" id="idd2dfa588f954d8a8d7c131ab63047a5_SubsequentEventsTermLoanBApplicableMarginDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_8b8c710b-08db-4751-aa22-d32ceadafd09" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBEuroRateLoanSpread_4e407f02-09d7-4236-9825-e4b74e140717" xlink:href="icui-20211231.xsd#icui_TermLoanBEuroRateLoanSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8b8c710b-08db-4751-aa22-d32ceadafd09" xlink:to="loc_icui_TermLoanBEuroRateLoanSpread_4e407f02-09d7-4236-9825-e4b74e140717" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBBaseRateLoanSpread_aab33583-4ce0-47bb-af0a-ea7ad1deb78d" xlink:href="icui-20211231.xsd#icui_TermLoanBBaseRateLoanSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8b8c710b-08db-4751-aa22-d32ceadafd09" xlink:to="loc_icui_TermLoanBBaseRateLoanSpread_aab33583-4ce0-47bb-af0a-ea7ad1deb78d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBInitialSpread_ec122530-9d09-46ad-8eb3-feb57c7c3223" xlink:href="icui-20211231.xsd#icui_TermLoanBInitialSpread"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_8b8c710b-08db-4751-aa22-d32ceadafd09" xlink:to="loc_icui_TermLoanBInitialSpread_ec122530-9d09-46ad-8eb3-feb57c7c3223" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_c9bfaacb-8dcd-4a3c-8eb4-053eb14580a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_8b8c710b-08db-4751-aa22-d32ceadafd09" xlink:to="loc_us-gaap_SubsequentEventTable_c9bfaacb-8dcd-4a3c-8eb4-053eb14580a0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_6ecff371-a16a-43fa-83e3-b08130c80b8d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_c9bfaacb-8dcd-4a3c-8eb4-053eb14580a0" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_6ecff371-a16a-43fa-83e3-b08130c80b8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_6ecff371-a16a-43fa-83e3-b08130c80b8d_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6ecff371-a16a-43fa-83e3-b08130c80b8d" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_6ecff371-a16a-43fa-83e3-b08130c80b8d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_580e3582-dd6f-4937-8f88-893ae0e9a65f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_6ecff371-a16a-43fa-83e3-b08130c80b8d" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_580e3582-dd6f-4937-8f88-893ae0e9a65f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_7f81f866-01b3-4c71-8dfe-f5006cfbd16c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_580e3582-dd6f-4937-8f88-893ae0e9a65f" xlink:to="loc_us-gaap_SubsequentEventMember_7f81f866-01b3-4c71-8dfe-f5006cfbd16c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBApplicableMarginAxis_a8a9eac2-13d6-464a-9203-40726f8b1b67" xlink:href="icui-20211231.xsd#icui_TermLoanBApplicableMarginAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_c9bfaacb-8dcd-4a3c-8eb4-053eb14580a0" xlink:to="loc_icui_TermLoanBApplicableMarginAxis_a8a9eac2-13d6-464a-9203-40726f8b1b67" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBApplicableMarginDomain_a8a9eac2-13d6-464a-9203-40726f8b1b67_default" xlink:href="icui-20211231.xsd#icui_TermLoanBApplicableMarginDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanBApplicableMarginAxis_a8a9eac2-13d6-464a-9203-40726f8b1b67" xlink:to="loc_icui_TermLoanBApplicableMarginDomain_a8a9eac2-13d6-464a-9203-40726f8b1b67_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBApplicableMarginDomain_63696b94-bdad-4477-a2a6-4ddd966e44f6" xlink:href="icui-20211231.xsd#icui_TermLoanBApplicableMarginDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanBApplicableMarginAxis_a8a9eac2-13d6-464a-9203-40726f8b1b67" xlink:to="loc_icui_TermLoanBApplicableMarginDomain_63696b94-bdad-4477-a2a6-4ddd966e44f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIIMemberMember_27283f12-b08f-46d5-b1d1-669aaa307648" xlink:href="icui-20211231.xsd#icui_PricingLevelIIMemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanBApplicableMarginDomain_63696b94-bdad-4477-a2a6-4ddd966e44f6" xlink:to="loc_icui_PricingLevelIIMemberMember_27283f12-b08f-46d5-b1d1-669aaa307648" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PricingLevelIMember_a7ea4173-7bae-47b8-bf52-dee4d6a20d38" xlink:href="icui-20211231.xsd#icui_PricingLevelIMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanBApplicableMarginDomain_63696b94-bdad-4477-a2a6-4ddd966e44f6" xlink:to="loc_icui_PricingLevelIMember_a7ea4173-7bae-47b8-bf52-dee4d6a20d38" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SECScheduleArticle1209ValuationandQualifyingAccountsDetails" xlink:type="simple" xlink:href="icui-20211231.xsd#SECScheduleArticle1209ValuationandQualifyingAccountsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SECScheduleArticle1209ValuationandQualifyingAccountsDetails" xlink:type="extended" id="i71dccdae10114ca590d5ca6cbb38a46a_SECScheduleArticle1209ValuationandQualifyingAccountsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_7ca6484e-522f-4ad8-937c-c925e6fe84f5" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MovementInValuationAllowancesAndReservesRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_7ca6484e-522f-4ad8-937c-c925e6fe84f5" xlink:to="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_998289bb-f8ed-4e5d-957c-bfaa51483c22" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesBalance_998289bb-f8ed-4e5d-957c-bfaa51483c22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_755bfca8-e341-4206-9bde-842196ce572a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToCostAndExpense_755bfca8-e341-4206-9bde-842196ce572a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_74202e3a-5904-4381-9f3b-5820fb210cd4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesChargedToOtherAccounts_74202e3a-5904-4381-9f3b-5820fb210cd4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesAdjustments_0e6660b6-c5ac-47e2-9150-d37624c3d18a" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesAdjustments_0e6660b6-c5ac-47e2-9150-d37624c3d18a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesBalance_3553b4cc-dc48-47e9-b42b-33951a707ca6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesBalance"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_WarrantyAndReturnReserveInventoryWriteOffs_a903127c-307a-432d-a2e1-3229e5549c3c" xlink:href="icui-20211231.xsd#icui_WarrantyAndReturnReserveInventoryWriteOffs"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_icui_WarrantyAndReturnReserveInventoryWriteOffs_a903127c-307a-432d-a2e1-3229e5549c3c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_WarrantyAndReturnReserveInventoryChargedToOtherAccounts_f022e6d2-4299-4e76-a28f-18aa729b34f9" xlink:href="icui-20211231.xsd#icui_WarrantyAndReturnReserveInventoryChargedToOtherAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_icui_WarrantyAndReturnReserveInventoryChargedToOtherAccounts_f022e6d2-4299-4e76-a28f-18aa729b34f9" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_WarrantyAndReturnReserveCosts_9985b3dc-c895-4caa-907b-6a7e723e7282" xlink:href="icui-20211231.xsd#icui_WarrantyAndReturnReserveCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_icui_WarrantyAndReturnReserveCosts_9985b3dc-c895-4caa-907b-6a7e723e7282" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_WarrantyAndReturnReserveInventory_1c2344dc-81f9-462d-87a8-63789d70f970" xlink:href="icui-20211231.xsd#icui_WarrantyAndReturnReserveInventory"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MovementInValuationAllowancesAndReservesRollForward_71de8118-7292-4a03-ad50-8ad42a8d8180" xlink:to="loc_icui_WarrantyAndReturnReserveInventory_1c2344dc-81f9-462d-87a8-63789d70f970" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e2baaa03-0718-4aef-bbd1-997a68b19eca" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ValuationAndQualifyingAccountsDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureLineItems_7ca6484e-522f-4ad8-937c-c925e6fe84f5" xlink:to="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e2baaa03-0718-4aef-bbd1-997a68b19eca" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_26cbc099-69af-464c-b149-2d3fcdd96903" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_srt_ValuationAndQualifyingAccountsDisclosureTable_e2baaa03-0718-4aef-bbd1-997a68b19eca" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_26cbc099-69af-464c-b149-2d3fcdd96903" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_26cbc099-69af-464c-b149-2d3fcdd96903_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_26cbc099-69af-464c-b149-2d3fcdd96903" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_26cbc099-69af-464c-b149-2d3fcdd96903_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowancesAndReservesDomain_5718ecd5-b5bc-4d2e-8191-3cf4f544ced0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowancesAndReservesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesTypeAxis_26cbc099-69af-464c-b149-2d3fcdd96903" xlink:to="loc_us-gaap_ValuationAllowancesAndReservesDomain_5718ecd5-b5bc-4d2e-8191-3cf4f544ced0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AllowanceForCreditLossMember_6570b451-948a-43e4-b96f-42bfad321a24" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllowanceForCreditLossMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_5718ecd5-b5bc-4d2e-8191-3cf4f544ced0" xlink:to="loc_us-gaap_AllowanceForCreditLossMember_6570b451-948a-43e4-b96f-42bfad321a24" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WarrantyReservesMember_3448eed1-e3e3-4c32-b26b-db3c83b58d72" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WarrantyReservesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_5718ecd5-b5bc-4d2e-8191-3cf4f544ced0" xlink:to="loc_us-gaap_WarrantyReservesMember_3448eed1-e3e3-4c32-b26b-db3c83b58d72" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_d5262aab-cf53-4489-a801-78a99238b2ad" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ValuationAllowancesAndReservesDomain_5718ecd5-b5bc-4d2e-8191-3cf4f544ced0" xlink:to="loc_us-gaap_ValuationAllowanceOfDeferredTaxAssetsMember_d5262aab-cf53-4489-a801-78a99238b2ad" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-roles-2021-01-31.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract" xlink:to="loc_us-gaap_OtherAssetsNoncurrent" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesNoncurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesNoncurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilities" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesNoncurrentAbstract" xlink:to="loc_us-gaap_OtherLiabilities" xlink:type="arc" order="0"/>
  </link:definitionLink>
</link:linkbase>
