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

<!--XBRL Document Created with Wdesk from Workiva-->
<!--Copyright 2022 Workiva-->
<!--r:b855b77c-6988-4216-8748-36632a973ac3,g:ab2a959a-be44-44c8-8165-c7a4fa090087-->
<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/CondensedConsolidatedBalanceSheets" xlink:type="simple" xlink:href="icui-20220630.xsd#CondensedConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended" id="i86f5cb385c5a4ac38b4fe613b0ab985a_CondensedConsolidatedBalanceSheets">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_b47d6a4d-667b-4938-afe9-1b946fc50d36" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" 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_b47d6a4d-667b-4938-afe9-1b946fc50d36" xlink:to="loc_us-gaap_AssetsAbstract_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_37a7468d-d97a-4293-af78-bf6967ba1e22" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_AssetsCurrentAbstract_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_dbe229dc-f1e0-4dc9-a9f8-36f60845ce66" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_dbe229dc-f1e0-4dc9-a9f8-36f60845ce66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_7ff64042-b935-4bd1-b063-23ad895ae038" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_7ff64042-b935-4bd1-b063-23ad895ae038" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_505767a9-adf0-42d8-941f-28941ed68cbd" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_505767a9-adf0-42d8-941f-28941ed68cbd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_c9a465a7-f6e8-4573-a647-746ba5e81017" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_c9a465a7-f6e8-4573-a647-746ba5e81017" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_8ac34480-0ef1-450b-9f63-bce2087e852a" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_InventoryNet_8ac34480-0ef1-450b-9f63-bce2087e852a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidTaxes_a127bf93-e190-4e05-9ca4-1433d09fac43" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_PrepaidTaxes_a127bf93-e190-4e05-9ca4-1433d09fac43" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_dc01b927-4fa0-4d1a-b132-f2520f7f8d7d" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_dc01b927-4fa0-4d1a-b132-f2520f7f8d7d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_109fd4a8-4f7d-4819-b7dd-590c9dbbd973" 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_37a7468d-d97a-4293-af78-bf6967ba1e22" xlink:to="loc_us-gaap_AssetsCurrent_109fd4a8-4f7d-4819-b7dd-590c9dbbd973" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_017ea2c3-e03a-4eab-a7b2-34fcc5011c59" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_017ea2c3-e03a-4eab-a7b2-34fcc5011c59" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_3a14c95e-af1e-449a-ad3e-8176adf5a91d" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_3a14c95e-af1e-449a-ad3e-8176adf5a91d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_2f851da1-bcae-4e54-b74b-11f88514b9c5" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_2f851da1-bcae-4e54-b74b-11f88514b9c5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_c39e9af7-6045-4f7d-b64f-11f297116d78" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_Goodwill_c39e9af7-6045-4f7d-b64f-11f297116d78" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_b529e28e-bf8c-4001-b8b2-a4d24fee699f" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_b529e28e-bf8c-4001-b8b2-a4d24fee699f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_940b6fc0-6770-40c0-a476-0194e5bdf472" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_940b6fc0-6770-40c0-a476-0194e5bdf472" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_c9d18569-1830-4caf-9ff0-e31aae3024e3" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_c9d18569-1830-4caf-9ff0-e31aae3024e3" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_3cd56acf-ed94-4d1a-bb8b-8ac681c155d9" 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_19a3a460-b03b-4845-82d3-09a51dd3e365" xlink:to="loc_us-gaap_Assets_3cd56acf-ed94-4d1a-bb8b-8ac681c155d9" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" 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_b47d6a4d-667b-4938-afe9-1b946fc50d36" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_d45bc681-da80-480b-81d2-012d6c5aedc5" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_39a113cd-cf53-4b4d-a808-dcb74dc65e42" 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_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_AccountsPayableCurrent_39a113cd-cf53-4b4d-a808-dcb74dc65e42" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_d24af433-0db4-4aea-88f0-9415b4278cb4" 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_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_d24af433-0db4-4aea-88f0-9415b4278cb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_e38100f5-eb40-4a94-b5b6-719d4e8c3e95" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_LongTermDebtCurrent_e38100f5-eb40-4a94-b5b6-719d4e8c3e95" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_0972bf76-22f7-4d6e-938e-633dab5cd66d" 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_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_0972bf76-22f7-4d6e-938e-633dab5cd66d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_aa1fd095-8ef3-4e5f-8b44-628a46cf955c" 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_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityCurrent_aa1fd095-8ef3-4e5f-8b44-628a46cf955c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_423f19c9-4f15-41f3-bf63-83a09607615a" 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_d45bc681-da80-480b-81d2-012d6c5aedc5" xlink:to="loc_us-gaap_LiabilitiesCurrent_423f19c9-4f15-41f3-bf63-83a09607615a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_6176f05f-c035-4c02-a2ba-b78d59d30673" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_6176f05f-c035-4c02-a2ba-b78d59d30673" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_17723f70-513b-470f-833a-f645236a36b8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_17723f70-513b-470f-833a-f645236a36b8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_a45a8b5a-090b-4304-a188-e751099c6a23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_a45a8b5a-090b-4304-a188-e751099c6a23" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_91e37836-7d6c-41c2-9d76-e7392d02295a" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_91e37836-7d6c-41c2-9d76-e7392d02295a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_ecd3bbbb-b418-46a4-b329-f95b914a507c" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_ecd3bbbb-b418-46a4-b329-f95b914a507c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_eac3a6e3-b66a-439b-8922-1d90e7776233" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_CommitmentsAndContingencies_eac3a6e3-b66a-439b-8922-1d90e7776233" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_5b112b06-12bc-4726-8d65-5a1e99c0c1a5" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_5b112b06-12bc-4726-8d65-5a1e99c0c1a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_14def67c-c973-4b3c-ba2d-a260014f33d5" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_CommonStockValue_14def67c-c973-4b3c-ba2d-a260014f33d5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_05dbfa36-0147-481a-984b-ecec707450a7" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_05dbfa36-0147-481a-984b-ecec707450a7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_dfeaacf2-32a6-4ca8-90db-f46f4d56e526" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_TreasuryStockValue_dfeaacf2-32a6-4ca8-90db-f46f4d56e526" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_993e5183-8b4c-4eeb-b799-7c6118fec20c" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_993e5183-8b4c-4eeb-b799-7c6118fec20c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a2c661aa-bed2-485f-b09e-4f9b526b39c5" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_a2c661aa-bed2-485f-b09e-4f9b526b39c5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_1dff8dec-2084-4966-b41b-2d6c0eb0040f" 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_afd812ba-bf52-4cd7-8a5f-7e3a61eb2a30" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_1dff8dec-2084-4966-b41b-2d6c0eb0040f" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_d571f69d-e03a-476c-b9a3-b6a09d9e5e24" 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_aec44b0a-6ff0-4cc3-b235-2b1b7f8289c1" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_d571f69d-e03a-476c-b9a3-b6a09d9e5e24" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_fcb892ae-6d72-42bd-990e-4a74e8943fd5" 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_b47d6a4d-667b-4938-afe9-1b946fc50d36" xlink:to="loc_us-gaap_StatementTable_fcb892ae-6d72-42bd-990e-4a74e8943fd5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_248599b4-550f-48f2-bdbe-575b67ad60a4" 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_fcb892ae-6d72-42bd-990e-4a74e8943fd5" xlink:to="loc_srt_StatementScenarioAxis_248599b4-550f-48f2-bdbe-575b67ad60a4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_248599b4-550f-48f2-bdbe-575b67ad60a4_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_248599b4-550f-48f2-bdbe-575b67ad60a4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_248599b4-550f-48f2-bdbe-575b67ad60a4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_b104f8c5-9095-4ec3-b235-b70e46901f9e" 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_248599b4-550f-48f2-bdbe-575b67ad60a4" xlink:to="loc_srt_ScenarioUnspecifiedDomain_b104f8c5-9095-4ec3-b235-b70e46901f9e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="icui-20220630.xsd#CondensedConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="extended" id="i5ef5fa9577d4493baddabf7fcd84adeb_CondensedConsolidatedStatementsofIncome">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_34a88730-726c-49f6-adde-fd3b44a8e8e8" 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_ad12ed62-5b36-43ca-a147-b6c10810a7a6" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_RevenuesAbstract_ad12ed62-5b36-43ca-a147-b6c10810a7a6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b726a3be-8274-405b-970b-b45df44875ac" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_ad12ed62-5b36-43ca-a147-b6c10810a7a6" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b726a3be-8274-405b-970b-b45df44875ac" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_0228241d-d212-4796-b54e-7cb5b4a177ff" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_ad12ed62-5b36-43ca-a147-b6c10810a7a6" xlink:to="loc_us-gaap_CostOfRevenue_0228241d-d212-4796-b54e-7cb5b4a177ff" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_c0db6e5a-8cca-48cc-aadd-4bef699d1dd1" 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_RevenuesAbstract_ad12ed62-5b36-43ca-a147-b6c10810a7a6" xlink:to="loc_us-gaap_GrossProfit_c0db6e5a-8cca-48cc-aadd-4bef699d1dd1" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_OperatingExpensesAbstract_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_255f406e-7a2f-43ba-b2d4-2ff6deb52528" 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_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_255f406e-7a2f-43ba-b2d4-2ff6deb52528" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_7e629245-9174-4978-9437-dd3ddc52c015" 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_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_7e629245-9174-4978-9437-dd3ddc52c015" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Restructuringandstrategictransaction_7a85c9e0-e314-43af-95c1-1c0fc3cced66" xlink:href="icui-20220630.xsd#icui_Restructuringandstrategictransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_icui_Restructuringandstrategictransaction_7a85c9e0-e314-43af-95c1-1c0fc3cced66" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_727299d3-2970-4a76-9e1c-8762f6de7810" 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_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_727299d3-2970-4a76-9e1c-8762f6de7810" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contractsettlement_34e5af69-13a9-457a-aa87-fafe84752ec6" xlink:href="icui-20220630.xsd#icui_Contractsettlement"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_icui_Contractsettlement_34e5af69-13a9-457a-aa87-fafe84752ec6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_942c6756-903a-42e9-b888-381d54b777ae" 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_f9eca9d7-e0fc-4c0c-83af-416ade2d6e49" xlink:to="loc_us-gaap_OperatingExpenses_942c6756-903a-42e9-b888-381d54b777ae" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_1b316604-26c9-4afa-baa7-71023e54bb06" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_OperatingIncomeLoss_1b316604-26c9-4afa-baa7-71023e54bb06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_1fb62884-1b7b-491a-a9c9-bc9e69fd1443" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_InterestExpense_1fb62884-1b7b-491a-a9c9-bc9e69fd1443" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_129aa3e3-49df-4d5f-8055-a482f2c95650" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_129aa3e3-49df-4d5f-8055-a482f2c95650" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_bdd7445c-5d82-47b6-9fab-af4af1c4b9f6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_bdd7445c-5d82-47b6-9fab-af4af1c4b9f6" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_594b278a-9e8f-49ac-974e-951fb74cf715" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_594b278a-9e8f-49ac-974e-951fb74cf715" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_56690e9d-a266-41ae-9254-ffca3aa7b0aa" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_ProfitLoss_56690e9d-a266-41ae-9254-ffca3aa7b0aa" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_8cd99568-f1b9-4601-a9cd-fc9e7cc8346f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_EarningsPerShareAbstract_8cd99568-f1b9-4601-a9cd-fc9e7cc8346f" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_cf7cac77-43d2-4995-b598-7d3b8c4bf542" 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_EarningsPerShareAbstract_8cd99568-f1b9-4601-a9cd-fc9e7cc8346f" xlink:to="loc_us-gaap_EarningsPerShareBasic_cf7cac77-43d2-4995-b598-7d3b8c4bf542" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_27318880-c35b-44a6-9221-c97741df3359" 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_EarningsPerShareAbstract_8cd99568-f1b9-4601-a9cd-fc9e7cc8346f" xlink:to="loc_us-gaap_EarningsPerShareDiluted_27318880-c35b-44a6-9221-c97741df3359" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bf5f4999-0fbe-4464-b434-2b4fe081ef52" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_bf5f4999-0fbe-4464-b434-2b4fe081ef52" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e80f349c-c8a0-4c92-ad46-8ba06ce83098" 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_bf5f4999-0fbe-4464-b434-2b4fe081ef52" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_e80f349c-c8a0-4c92-ad46-8ba06ce83098" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_6a70263f-c753-48e4-bf76-b2254459609c" 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_bf5f4999-0fbe-4464-b434-2b4fe081ef52" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_6a70263f-c753-48e4-bf76-b2254459609c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_e7fa286e-8eb0-4add-8f65-2e0cb5d0ff5a" 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_34a88730-726c-49f6-adde-fd3b44a8e8e8" xlink:to="loc_us-gaap_StatementTable_e7fa286e-8eb0-4add-8f65-2e0cb5d0ff5a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_ffb8e771-ded6-489e-ad15-a53e512a9fa0" 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_e7fa286e-8eb0-4add-8f65-2e0cb5d0ff5a" xlink:to="loc_srt_ProductOrServiceAxis_ffb8e771-ded6-489e-ad15-a53e512a9fa0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_ffb8e771-ded6-489e-ad15-a53e512a9fa0_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_ffb8e771-ded6-489e-ad15-a53e512a9fa0" xlink:to="loc_srt_ProductsAndServicesDomain_ffb8e771-ded6-489e-ad15-a53e512a9fa0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_cbba0a0d-d93a-4236-ae92-aa7547de0ea5" 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_ffb8e771-ded6-489e-ad15-a53e512a9fa0" xlink:to="loc_srt_ProductsAndServicesDomain_cbba0a0d-d93a-4236-ae92-aa7547de0ea5" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="icui-20220630.xsd#CondensedConsolidatedStatementsofComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="extended" id="i1d67d2580ca54127925d6e1b384b25ca_CondensedConsolidatedStatementsofComprehensiveIncome">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e24af8b1-fc00-4891-81a1-6653ee46471e" 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_ProfitLoss_df0063d8-4988-4ca4-a43b-7578dd5e1e33" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e24af8b1-fc00-4891-81a1-6653ee46471e" xlink:to="loc_us-gaap_ProfitLoss_df0063d8-4988-4ca4-a43b-7578dd5e1e33" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e24af8b1-fc00-4891-81a1-6653ee46471e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_5e505edb-8695-4516-9d65-39f2ef2c0c15" 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_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_5e505edb-8695-4516-9d65-39f2ef2c0c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_a8038e84-f611-4347-821d-cdbd3f94d95e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_a8038e84-f611-4347-821d-cdbd3f94d95e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_4978692d-d14d-4702-a70d-2f3982ea79fa" 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_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_4978692d-d14d-4702-a70d-2f3982ea79fa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8792d343-836d-4d2e-bb08-9de78d15b3fd" 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_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_e2cdffbd-73b7-4a48-8bed-8029b3217809" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_8792d343-836d-4d2e-bb08-9de78d15b3fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_e217b3e7-1395-413b-a4d5-35a25c8217b8" 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_e24af8b1-fc00-4891-81a1-6653ee46471e" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_e217b3e7-1395-413b-a4d5-35a25c8217b8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_941dc6e7-a8f9-4718-a3b9-7bdf58698478" 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_e24af8b1-fc00-4891-81a1-6653ee46471e" xlink:to="loc_us-gaap_StatementTable_941dc6e7-a8f9-4718-a3b9-7bdf58698478" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b" 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_941dc6e7-a8f9-4718-a3b9-7bdf58698478" xlink:to="loc_srt_StatementScenarioAxis_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b_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_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b" xlink:to="loc_srt_ScenarioUnspecifiedDomain_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_117d62f2-64c6-4a16-b966-7cfa62235a9b" 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_0f1eeaaf-dd4f-4a1d-a91b-266288c3877b" xlink:to="loc_srt_ScenarioUnspecifiedDomain_117d62f2-64c6-4a16-b966-7cfa62235a9b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofStockholdersEquityStatement" xlink:type="simple" xlink:href="icui-20220630.xsd#CondensedConsolidatedStatementsofStockholdersEquityStatement"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofStockholdersEquityStatement" xlink:type="extended" id="i2a31928ee9aa4b3aa70817c9aa88000f_CondensedConsolidatedStatementsofStockholdersEquityStatement">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_9380ff01-7015-4ba2-ab2c-5238e1287fd1" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" 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_9380ff01-7015-4ba2-ab2c-5238e1287fd1" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_4e7ee1f4-eabb-42a4-b7fc-05630b2a5635" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_4e7ee1f4-eabb-42a4-b7fc-05630b2a5635" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_97f8edaf-7e7c-4b19-88e1-cf8f8bbdddb9" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_StockholdersEquity_97f8edaf-7e7c-4b19-88e1-cf8f8bbdddb9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e17ab5f4-3e86-475e-9585-d7aaa6ae9b23" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e17ab5f4-3e86-475e-9585-d7aaa6ae9b23" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_778512ea-1c5c-42aa-ae4b-184fb8d4ec0d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_778512ea-1c5c-42aa-ae4b-184fb8d4ec0d" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_2b36e847-6a9b-4740-8600-745c46a9defc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_2b36e847-6a9b-4740-8600-745c46a9defc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_7285c145-f0f1-4c65-92cb-ec2ae0b08e3f" 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_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_7285c145-f0f1-4c65-92cb-ec2ae0b08e3f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_59792255-898e-429c-adf7-e7e780a40e71" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_59792255-898e-429c-adf7-e7e780a40e71" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_89e3ef3b-f002-4a67-a18e-81855c03d1e6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueAcquisitions_89e3ef3b-f002-4a67-a18e-81855c03d1e6" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_031f591d-3e7c-410e-a1d7-a52120ba6c0f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesAcquisitions_031f591d-3e7c-410e-a1d7-a52120ba6c0f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e61ca260-8bc9-4aeb-8382-94a194046e24" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_e61ca260-8bc9-4aeb-8382-94a194046e24" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_88d21e57-0230-4a89-8036-66add0212cce" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_88d21e57-0230-4a89-8036-66add0212cce" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_396321ee-b439-441a-b758-54c4060d078d" 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_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_NetIncomeLoss_396321ee-b439-441a-b758-54c4060d078d" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_5c01d486-d119-4a1a-863c-839280220f16" 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_7089df9f-c281-41cc-910e-fc7f00ecd58f" 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_OtherComprehensiveIncomeLossNetOfTax_aa494eb1-0d0e-461b-86c1-f15fec4886b2" 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_IncreaseDecreaseInStockholdersEquityRollForward_957036ee-ae8d-4005-91c8-0cb074fd2bc3" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_aa494eb1-0d0e-461b-86c1-f15fec4886b2" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_7a4f49a1-8a9a-4aa0-8fcc-82a31e0b19fd" 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_9380ff01-7015-4ba2-ab2c-5238e1287fd1" xlink:to="loc_us-gaap_StatementTable_7a4f49a1-8a9a-4aa0-8fcc-82a31e0b19fd" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_937cb51b-581e-4c48-bdb1-cfb3323e3906" 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_7a4f49a1-8a9a-4aa0-8fcc-82a31e0b19fd" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_937cb51b-581e-4c48-bdb1-cfb3323e3906" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_937cb51b-581e-4c48-bdb1-cfb3323e3906_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_937cb51b-581e-4c48-bdb1-cfb3323e3906" xlink:to="loc_us-gaap_EquityComponentDomain_937cb51b-581e-4c48-bdb1-cfb3323e3906_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_130bdc9f-0020-4fe7-90a7-3b26102b92c9" 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_937cb51b-581e-4c48-bdb1-cfb3323e3906" xlink:to="loc_us-gaap_EquityComponentDomain_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CommonStockSharesMember_b9f1d928-f080-4b58-b855-4c024c13fddc" xlink:href="icui-20220630.xsd#icui_CommonStockSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_icui_CommonStockSharesMember_b9f1d928-f080-4b58-b855-4c024c13fddc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_f0637149-1f75-4ec1-aaef-bc103c6065c6" 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_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_us-gaap_CommonStockMember_f0637149-1f75-4ec1-aaef-bc103c6065c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_d3fbc4e0-ee25-465b-9cee-249e1d2cd7ac" 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_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_d3fbc4e0-ee25-465b-9cee-249e1d2cd7ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockMember_375e4e6b-070f-4e94-93af-df6dd430d81d" 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_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_us-gaap_TreasuryStockMember_375e4e6b-070f-4e94-93af-df6dd430d81d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_42b2a62e-d02c-4f29-8a6c-1c83371f91d7" 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_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_us-gaap_RetainedEarningsMember_42b2a62e-d02c-4f29-8a6c-1c83371f91d7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c2c430cd-7d32-42e9-b43b-e169c7f34744" 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_130bdc9f-0020-4fe7-90a7-3b26102b92c9" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_c2c430cd-7d32-42e9-b43b-e169c7f34744" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="icui-20220630.xsd#CondensedConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="extended" id="ie04b20be52eb4a528f60823f32d7f1de_CondensedConsolidatedStatementsofCashFlows">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_45fd7634-5e29-4a42-954f-1faa078bd875" 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_1a6a4fb7-ce78-431c-a29d-3b136a6ff77f" 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_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_1a6a4fb7-ce78-431c-a29d-3b136a6ff77f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_a8c409c1-c114-4848-9949-e30bb5048220" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashAndCashEquivalentsPeriodIncreaseDecreaseAbstract_1a6a4fb7-ce78-431c-a29d-3b136a6ff77f" xlink:to="loc_us-gaap_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_a8c409c1-c114-4848-9949-e30bb5048220" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" 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_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_a8c409c1-c114-4848-9949-e30bb5048220" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_41783692-9060-439a-89a6-8f150b91bb18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_ProfitLoss_41783692-9060-439a-89a6-8f150b91bb18" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_520e46bf-fcc9-4b4e-a2d3-698ec362764f" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_520e46bf-fcc9-4b4e-a2d3-698ec362764f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_AmortizationOfInventoryStepUp_885052bd-be2a-425e-8aa8-1dee111df9b0" xlink:href="icui-20220630.xsd#icui_AmortizationOfInventoryStepUp"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_icui_AmortizationOfInventoryStepUp_885052bd-be2a-425e-8aa8-1dee111df9b0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_e4e6ddd6-3a6c-444d-8d2c-e6d82187ca1c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_e4e6ddd6-3a6c-444d-8d2c-e6d82187ca1c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_5b655420-2d10-4475-801f-4a72ab009a00" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_5b655420-2d10-4475-801f-4a72ab009a00" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ProvisionForWarrantyAndReturns_697e5cf0-23fd-4500-b9c9-08d79c2c3d58" xlink:href="icui-20220630.xsd#icui_ProvisionForWarrantyAndReturns"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_icui_ProvisionForWarrantyAndReturns_697e5cf0-23fd-4500-b9c9-08d79c2c3d58" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_c34f2493-901a-4ae3-ade6-f2d2915d422c" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_ShareBasedCompensation_c34f2493-901a-4ae3-ade6-f2d2915d422c" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_3c973b67-21d6-4f5b-86bb-f9d3224c0e7e" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_3c973b67-21d6-4f5b-86bb-f9d3224c0e7e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_a44bab24-c18e-4e00-a2c6-4e92c55e476e" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_a44bab24-c18e-4e00-a2c6-4e92c55e476e" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_ebc96f8b-15f2-471e-9bfe-01dd8830a7a2" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_ebc96f8b-15f2-471e-9bfe-01dd8830a7a2" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5807f66c-bcb1-4387-a7bb-ee66bbfa5517" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_5807f66c-bcb1-4387-a7bb-ee66bbfa5517" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Sparepartsusage_bc40b1a5-8b3f-40e9-940e-767a6652eef4" xlink:href="icui-20220630.xsd#icui_Sparepartsusage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_icui_Sparepartsusage_bc40b1a5-8b3f-40e9-940e-767a6652eef4" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_521a3e3c-893c-4eea-ad98-875cfa78aae9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_521a3e3c-893c-4eea-ad98-875cfa78aae9" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_417252f5-306a-456d-9b22-f1068756fa55" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_417252f5-306a-456d-9b22-f1068756fa55" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_1e88bd71-6525-411a-bbdf-98d75602a160" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_1e88bd71-6525-411a-bbdf-98d75602a160" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2cf61349-debf-4b4c-9276-dbe62e24dd5f" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_2cf61349-debf-4b4c-9276-dbe62e24dd5f" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_9ccb93aa-9b9f-42a0-adf8-8864f2f2f98e" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_9ccb93aa-9b9f-42a0-adf8-8864f2f2f98e" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_f016c56f-1297-49cf-97c4-a15283dd1125" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_f016c56f-1297-49cf-97c4-a15283dd1125" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_7c222259-5621-4b10-a885-1d33f84ba28f" 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_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_7c222259-5621-4b10-a885-1d33f84ba28f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_0b281f78-c42e-4fa9-b1c9-1e5893ae65d7" xlink:href="icui-20220630.xsd#icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_0b281f78-c42e-4fa9-b1c9-1e5893ae65d7" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4c3aeafa-fa46-45ff-8a5f-91940a9df3cb" 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_NetCashProvidedByUsedInOperatingActivitiesAbstract_997021da-e635-4e6e-9b03-2879001daf08" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_4c3aeafa-fa46-45ff-8a5f-91940a9df3cb" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_df72a101-9ea9-41b0-849f-713656b85a0f" 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_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_a8c409c1-c114-4848-9949-e30bb5048220" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_a7a79476-0bdd-4772-aeac-04d2ce1f9465" 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_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_a7a79476-0bdd-4772-aeac-04d2ce1f9465" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_66e2144f-1a52-4c2b-b589-6dc6aff69ed8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_66e2144f-1a52-4c2b-b589-6dc6aff69ed8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_44c8d1dd-09b3-4555-b39f-fec08d5d48ef" 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_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_44c8d1dd-09b3-4555-b39f-fec08d5d48ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireMarketableSecurities_a82aa1cc-d5fd-47e5-99af-f72162368e3e" 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_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_PaymentsToAcquireMarketableSecurities_a82aa1cc-d5fd-47e5-99af-f72162368e3e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_6884046e-6ecf-4172-9aa0-742e4c3948fc" 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_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_6884046e-6ecf-4172-9aa0-742e4c3948fc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_021c46e8-35c1-4e55-9c89-9dd97d1e5a8d" 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_NetCashProvidedByUsedInInvestingActivitiesAbstract_df72a101-9ea9-41b0-849f-713656b85a0f" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_021c46e8-35c1-4e55-9c89-9dd97d1e5a8d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" 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_CashPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_a8c409c1-c114-4848-9949-e30bb5048220" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ProceedsFromIssuanceOfLongTermDebtNetOfLenderDebtIssuanceCosts_7a898c82-2f97-48cd-8c54-c9660829394f" xlink:href="icui-20220630.xsd#icui_ProceedsFromIssuanceOfLongTermDebtNetOfLenderDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_icui_ProceedsFromIssuanceOfLongTermDebtNetOfLenderDebtIssuanceCosts_7a898c82-2f97-48cd-8c54-c9660829394f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_f9648fc9-4ba0-4001-87b7-4b7d7befb638" 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_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_f9648fc9-4ba0-4001-87b7-4b7d7befb638" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsOfDebtIssuanceCosts_75636ddc-73e0-41ac-a5a3-744cee8746ef" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsOfDebtIssuanceCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_PaymentsOfDebtIssuanceCosts_75636ddc-73e0-41ac-a5a3-744cee8746ef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_a28b5d61-43fd-402f-a7ab-bafe182bb539" 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_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_a28b5d61-43fd-402f-a7ab-bafe182bb539" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_c00e223a-03c9-447a-82f4-cef1739caf47" 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_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_c00e223a-03c9-447a-82f4-cef1739caf47" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_0e3d1722-0ad2-47e9-8c98-f5aa100159da" 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_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_0e3d1722-0ad2-47e9-8c98-f5aa100159da" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_a6cd387d-ccfa-4425-b2e8-9c040fb5f787" 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_NetCashProvidedByUsedInFinancingActivitiesAbstract_8b83f510-e821-4344-aa9c-837512b3a423" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_a6cd387d-ccfa-4425-b2e8-9c040fb5f787" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_14a96eb7-ca75-4b4a-9e1a-fa4e859597c1" 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_1a6a4fb7-ce78-431c-a29d-3b136a6ff77f" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAbstract_14a96eb7-ca75-4b4a-9e1a-fa4e859597c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_bf2254d8-0032-4c0d-933a-34cb310eb3b1" 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_14a96eb7-ca75-4b4a-9e1a-fa4e859597c1" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_bf2254d8-0032-4c0d-933a-34cb310eb3b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_fd7a0bac-f7f4-4caa-8135-a4aa0d8e2f7e" 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_StatementLineItems_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_fd7a0bac-f7f4-4caa-8135-a4aa0d8e2f7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_964fab85-22ca-4d5d-b847-498f9d7b44c4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_964fab85-22ca-4d5d-b847-498f9d7b44c4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_7cf151ab-1e86-453a-b217-9db05bea8956" 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_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_7cf151ab-1e86-453a-b217-9db05bea8956" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_13260465-c803-4c3b-8d95-f07875dde7da" 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_SupplementalCashFlowInformationAbstract_7cf151ab-1e86-453a-b217-9db05bea8956" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_13260465-c803-4c3b-8d95-f07875dde7da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" 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_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueOfAssetsAcquired_1705a17b-8d65-4e53-9ebe-6148e16db0ed" 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_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_us-gaap_FairValueOfAssetsAcquired_1705a17b-8d65-4e53-9ebe-6148e16db0ed" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bb648516-de30-4ac2-8b67-944dd9a1e442" 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_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_bb648516-de30-4ac2-8b67-944dd9a1e442" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_334ec3fb-35ca-478a-8ec5-a99dba2f69fc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredEquityInterestsIssuedAndIssuable_334ec3fb-35ca-478a-8ec5-a99dba2f69fc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationAllAcquisitions_45b6ae54-01ba-4e4a-a34f-3007bafad9f8" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationAllAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_icui_ContingentConsiderationAllAcquisitions_45b6ae54-01ba-4e4a-a34f-3007bafad9f8" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GoodwillAcquiredDuringPeriodAllAcquisitions_d891d4ff-5702-4671-9f2b-f6d993ee6d75" xlink:href="icui-20220630.xsd#icui_GoodwillAcquiredDuringPeriodAllAcquisitions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_icui_GoodwillAcquiredDuringPeriodAllAcquisitions_d891d4ff-5702-4671-9f2b-f6d993ee6d75" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAssumed1_ac175cba-38a4-46e9-a44f-6a4c1bb94aec" 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_fff0fc93-228f-483a-9b70-9de2f77b260e" xlink:to="loc_us-gaap_LiabilitiesAssumed1_ac175cba-38a4-46e9-a44f-6a4c1bb94aec" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_89554f07-9282-439e-ba0a-f7b1f5d1d8d9" 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_45fd7634-5e29-4a42-954f-1faa078bd875" xlink:to="loc_us-gaap_StatementTable_89554f07-9282-439e-ba0a-f7b1f5d1d8d9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_35fddf0b-5dd1-404a-a419-8072f42abbff" 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_89554f07-9282-439e-ba0a-f7b1f5d1d8d9" xlink:to="loc_srt_StatementScenarioAxis_35fddf0b-5dd1-404a-a419-8072f42abbff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_35fddf0b-5dd1-404a-a419-8072f42abbff_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_35fddf0b-5dd1-404a-a419-8072f42abbff" xlink:to="loc_srt_ScenarioUnspecifiedDomain_35fddf0b-5dd1-404a-a419-8072f42abbff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_b25b66b6-8c11-4cb4-9191-65e745472c34" 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_35fddf0b-5dd1-404a-a419-8072f42abbff" xlink:to="loc_srt_ScenarioUnspecifiedDomain_b25b66b6-8c11-4cb4-9191-65e745472c34" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_705bbee2-1e9f-42aa-b812-275248b0eb20" 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_89554f07-9282-439e-ba0a-f7b1f5d1d8d9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_705bbee2-1e9f-42aa-b812-275248b0eb20" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_705bbee2-1e9f-42aa-b812-275248b0eb20_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_705bbee2-1e9f-42aa-b812-275248b0eb20" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_705bbee2-1e9f-42aa-b812-275248b0eb20_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_258008f4-e75e-4904-a52c-0007ef4a7e89" 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_705bbee2-1e9f-42aa-b812-275248b0eb20" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_258008f4-e75e-4904-a52c-0007ef4a7e89" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsForeignInfusionDistributorDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#BusinessCombinationsandAssetAcquisitionsForeignInfusionDistributorDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsForeignInfusionDistributorDetails" xlink:type="extended" id="i7d697e6696ce4856a554490dd1d62337_BusinessCombinationsandAssetAcquisitionsForeignInfusionDistributorDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_2a1f681b-7017-4791-bdb1-516112e80390" 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_PaymentsToAcquireBusinessesGross_8f14e07d-14e5-4472-a757-398cd0bf9a37" 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_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_8f14e07d-14e5-4472-a757-398cd0bf9a37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_a0abca0a-a9b0-4fc0-aa07-5af8a07c25e6" xlink:href="icui-20220630.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_icui_Contingentconsiderationgross_a0abca0a-a9b0-4fc0-aa07-5af8a07c25e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossST_f47e346c-36cc-4092-b3f4-b4d70148166d" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossST"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_icui_ContingentConsiderationGrossST_f47e346c-36cc-4092-b3f4-b4d70148166d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossLT_83eb5e0e-dd6e-4012-aa11-04fe66f24076" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossLT"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_icui_ContingentConsiderationGrossLT_83eb5e0e-dd6e-4012-aa11-04fe66f24076" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationConsiderationHoldbackLiability_fa0328c7-40e1-4ab4-8086-c49c977f6920" xlink:href="icui-20220630.xsd#icui_BusinessCombinationConsiderationHoldbackLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_icui_BusinessCombinationConsiderationHoldbackLiability_fa0328c7-40e1-4ab4-8086-c49c977f6920" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d6c0e35f-e274-4bca-871a-d99056fde187" 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_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_d6c0e35f-e274-4bca-871a-d99056fde187" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_189b68d7-6cd5-40f4-94af-a3dc3011a492" 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_2a1f681b-7017-4791-bdb1-516112e80390" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_189b68d7-6cd5-40f4-94af-a3dc3011a492" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_93689f38-b202-4265-bc40-a4dd9505aeb9" 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_189b68d7-6cd5-40f4-94af-a3dc3011a492" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_93689f38-b202-4265-bc40-a4dd9505aeb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_93689f38-b202-4265-bc40-a4dd9505aeb9_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_93689f38-b202-4265-bc40-a4dd9505aeb9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_93689f38-b202-4265-bc40-a4dd9505aeb9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c7d27d74-7f92-44f8-a701-8e907d0c49a7" 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_93689f38-b202-4265-bc40-a4dd9505aeb9" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c7d27d74-7f92-44f8-a701-8e907d0c49a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_2724a2c1-1134-4408-8a2a-0b2b72654267" xlink:href="icui-20220630.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_c7d27d74-7f92-44f8-a701-8e907d0c49a7" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_2724a2c1-1134-4408-8a2a-0b2b72654267" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#BusinessCombinationsandAssetAcquisitionsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsDetails" xlink:type="extended" id="ib52aea07f82944149a5093189b1ab499_BusinessCombinationsandAssetAcquisitionsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_c813084d-cb83-4f03-9ec2-4d712421815d" 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_fd4113db-b1cd-4b2a-81a0-8e217d2f1ac6" 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_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired_fd4113db-b1cd-4b2a-81a0-8e217d2f1ac6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationConsiderationTransferredCash_21576ea0-d49a-4372-bc94-a6352c4fb2fa" xlink:href="icui-20220630.xsd#icui_BusinessCombinationConsiderationTransferredCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_icui_BusinessCombinationConsiderationTransferredCash_21576ea0-d49a-4372-bc94-a6352c4fb2fa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_51025daa-cdf3-4329-b3c9-4c572e4a672b" 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_BusinessAcquisitionLineItems_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_51025daa-cdf3-4329-b3c9-4c572e4a672b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_016243e3-9533-4f76-a2b6-476882828cde" 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_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityNoncurrent_016243e3-9533-4f76-a2b6-476882828cde" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MinimumStockPriceTargetForEarnOutPayment_0981f38f-3e5c-4823-80b3-9075e444a4bd" xlink:href="icui-20220630.xsd#icui_MinimumStockPriceTargetForEarnOutPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_icui_MinimumStockPriceTargetForEarnOutPayment_0981f38f-3e5c-4823-80b3-9075e444a4bd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RequiredShareHoldingOfStockIssuedAtAcquisition_b927e3b4-9d21-4fa7-85c0-aee73561565f" xlink:href="icui-20220630.xsd#icui_RequiredShareHoldingOfStockIssuedAtAcquisition"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_icui_RequiredShareHoldingOfStockIssuedAtAcquisition_b927e3b4-9d21-4fa7-85c0-aee73561565f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_ae921024-d9f1-4cb7-b85b-ead083624aa9" 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_c813084d-cb83-4f03-9ec2-4d712421815d" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_ae921024-d9f1-4cb7-b85b-ead083624aa9" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_639142bb-47fc-4b01-ab2e-c91ef22853bd" 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_ae921024-d9f1-4cb7-b85b-ead083624aa9" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_639142bb-47fc-4b01-ab2e-c91ef22853bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_639142bb-47fc-4b01-ab2e-c91ef22853bd_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_639142bb-47fc-4b01-ab2e-c91ef22853bd" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_639142bb-47fc-4b01-ab2e-c91ef22853bd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cbd60a2b-9787-49f9-818a-19e094f3555a" 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_639142bb-47fc-4b01-ab2e-c91ef22853bd" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cbd60a2b-9787-49f9-818a-19e094f3555a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_1dc12d88-1aae-4e94-8c57-520d4589fd7c" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_cbd60a2b-9787-49f9-818a-19e094f3555a" xlink:to="loc_icui_SmithsMedicalMember_1dc12d88-1aae-4e94-8c57-520d4589fd7c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsSmithsMedicalDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#BusinessCombinationsandAssetAcquisitionsSmithsMedicalDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsSmithsMedicalDetails" xlink:type="extended" id="iee9f5d62af8e427ca2cadea24bd8ff87_BusinessCombinationsandAssetAcquisitionsSmithsMedicalDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" 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_PaymentsToAcquireBusinessesGross_3544d5cb-8d7c-47f8-9f98-ceaa0a524b55" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesGross_3544d5cb-8d7c-47f8-9f98-ceaa0a524b55" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_67e68a2e-45d8-444c-8086-4cae87049edf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_67e68a2e-45d8-444c-8086-4cae87049edf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_eb976a85-3c08-40a4-9cd9-d64f330bbdee" 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_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableNumberOfSharesIssued_eb976a85-3c08-40a4-9cd9-d64f330bbdee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionSharePrice_b0cc08f3-4fc2-4138-862b-1fa82261db8d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionSharePrice"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessAcquisitionSharePrice_b0cc08f3-4fc2-4138-862b-1fa82261db8d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_8518f7d2-5feb-4f79-8d0a-0f29b4a0dcbf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessAcquisitionEquityInterestIssuedOrIssuableValueAssigned_8518f7d2-5feb-4f79-8d0a-0f29b4a0dcbf" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_2dcdeca1-89b5-4196-b9ea-da03008d37c8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCashAndEquivalents_2dcdeca1-89b5-4196-b9ea-da03008d37c8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_a5d9176a-baa1-4e68-becf-caf37cb22e18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsReceivables_a5d9176a-baa1-4e68-becf-caf37cb22e18" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_e515d6ed-5301-47a6-bab6-6c25b9e02889" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedInventory_e515d6ed-5301-47a6-bab6-6c25b9e02889" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_96ae9486-f708-46bd-a166-3b6661478698" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentAssetsPrepaidExpenseAndOtherAssets_96ae9486-f708-46bd-a166-3b6661478698" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_3b630478-df1c-4d10-bebc-1c5ff3378bcf" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedPropertyPlantAndEquipment_3b630478-df1c-4d10-bebc-1c5ff3378bcf" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationRecognizedIdentifiableAssetAcquiredAndLiabilityAssumed_973c11a6-ebf1-4bda-bf4a-4ef5658251ab" xlink:href="icui-20220630.xsd#icui_BusinessCombinationRecognizedIdentifiableAssetAcquiredAndLiabilityAssumed"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_icui_BusinessCombinationRecognizedIdentifiableAssetAcquiredAndLiabilityAssumed_973c11a6-ebf1-4bda-bf4a-4ef5658251ab" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_afe28f6a-ec99-47e5-b93f-a6dfd9f17373" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_afe28f6a-ec99-47e5-b93f-a6dfd9f17373" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_7d3b95ec-57a4-4355-a7ff-f83ef0affdf2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxAssets_7d3b95ec-57a4-4355-a7ff-f83ef0affdf2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_4c60ea2c-75d1-4e5a-bcd8-b9d7137d3f0d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedOtherNoncurrentAssets_4c60ea2c-75d1-4e5a-bcd8-b9d7137d3f0d" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_74bb003b-b4c8-4b93-869d-a136c90f1b14" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilitiesAccountsPayable_74bb003b-b4c8-4b93-869d-a136c90f1b14" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_63e24df1-8840-4920-84d7-4aa8656af46e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedCurrentLiabilities_63e24df1-8840-4920-84d7-4aa8656af46e" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationsIdentifiedAssumedLiabilitiesRecognizedIncomeTaxPayable_a5b8679b-3ba0-4293-a844-6f0a02024f8a" xlink:href="icui-20220630.xsd#icui_BusinessCombinationsIdentifiedAssumedLiabilitiesRecognizedIncomeTaxPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_icui_BusinessCombinationsIdentifiedAssumedLiabilitiesRecognizedIncomeTaxPayable_a5b8679b-3ba0-4293-a844-6f0a02024f8a" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_ece63125-a3cb-4f09-88a0-fdbab6a8e700" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNoncurrentLiabilitiesOther_ece63125-a3cb-4f09-88a0-fdbab6a8e700" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_c5543bd1-8e9b-4fcb-b45c-59a48a97d315" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedDeferredTaxLiabilities_c5543bd1-8e9b-4fcb-b45c-59a48a97d315" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_ed0b0ea0-3950-4034-a3c3-4f38cdfbece5" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedNet_ed0b0ea0-3950-4034-a3c3-4f38cdfbece5" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_BusinessCombinationGoodwillNonDeductible_ece1c70c-2fc8-46d9-9b56-32e8fa0610fd" xlink:href="icui-20220630.xsd#icui_BusinessCombinationGoodwillNonDeductible"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_icui_BusinessCombinationGoodwillNonDeductible_ece1c70c-2fc8-46d9-9b56-32e8fa0610fd" xlink:type="arc" order="20"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ed73875-ed63-4e12-8355-21de1c7f0024" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferred1_5ed73875-ed63-4e12-8355-21de1c7f0024" xlink:type="arc" order="21"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_e1067a87-8c3f-48f8-95d8-07cd384b48a3" 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_BusinessAcquisitionLineItems_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_AcquiredFiniteLivedIntangibleAssetsWeightedAverageUsefulLife_e1067a87-8c3f-48f8-95d8-07cd384b48a3" xlink:type="arc" order="22"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_652c3d13-f460-4ae6-bfd5-b080c1391262" 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_2fda2576-23a7-4de3-84a4-ce2b19dbe3a5" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_652c3d13-f460-4ae6-bfd5-b080c1391262" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_9d272a00-3778-4a4f-b56d-7638bb5a52bb" 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_652c3d13-f460-4ae6-bfd5-b080c1391262" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_9d272a00-3778-4a4f-b56d-7638bb5a52bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9d272a00-3778-4a4f-b56d-7638bb5a52bb_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_9d272a00-3778-4a4f-b56d-7638bb5a52bb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_9d272a00-3778-4a4f-b56d-7638bb5a52bb_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a810f65-9a91-460e-a932-95ea01db00fd" 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_9d272a00-3778-4a4f-b56d-7638bb5a52bb" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a810f65-9a91-460e-a932-95ea01db00fd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_2e13f578-1f86-4f53-aa14-b771cf6f96bb" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5a810f65-9a91-460e-a932-95ea01db00fd" xlink:to="loc_icui_SmithsMedicalMember_2e13f578-1f86-4f53-aa14-b771cf6f96bb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_35404ca2-dfaa-4fc8-9462-39334bc9b81e" 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_ScheduleOfBusinessAcquisitionsByAcquisitionTable_652c3d13-f460-4ae6-bfd5-b080c1391262" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_35404ca2-dfaa-4fc8-9462-39334bc9b81e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_35404ca2-dfaa-4fc8-9462-39334bc9b81e_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_35404ca2-dfaa-4fc8-9462-39334bc9b81e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_35404ca2-dfaa-4fc8-9462-39334bc9b81e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" 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_35404ca2-dfaa-4fc8-9462-39334bc9b81e" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_0a4c3397-c654-4ad8-aaa9-42ed97cce626" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_CustomerRelationshipsMember_0a4c3397-c654-4ad8-aaa9-42ed97cce626" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_DevelopedTechnologyMember_159dff12-4423-40d1-919e-73e3cb283db0" xlink:href="icui-20220630.xsd#icui_DevelopedTechnologyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_icui_DevelopedTechnologyMember_159dff12-4423-40d1-919e-73e3cb283db0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksAndTradeNamesMember_51239555-d53f-4e90-b889-72275af4a925" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TrademarksAndTradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_TrademarksAndTradeNamesMember_51239555-d53f-4e90-b889-72275af4a925" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_fc2eb94b-2003-4ec3-9c5b-d9b7b74d6001" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_fc2eb94b-2003-4ec3-9c5b-d9b7b74d6001" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_eca4e4ad-746e-4730-b0f1-d30ffc50ae31" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TechnologyBasedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_TechnologyBasedIntangibleAssetsMember_eca4e4ad-746e-4730-b0f1-d30ffc50ae31" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SoftwareDevelopmentMember_4e909076-8117-4eda-89fb-13e3275eefe0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SoftwareDevelopmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_SoftwareDevelopmentMember_4e909076-8117-4eda-89fb-13e3275eefe0" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_0d02bc01-44ed-4a71-b182-930da175fb0d" 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_ebbe790a-ef53-4c18-8cf6-372b5fca9a74" xlink:to="loc_us-gaap_TrademarksMember_0d02bc01-44ed-4a71-b182-930da175fb0d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsSmithsMedicalProFormaDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#BusinessCombinationsandAssetAcquisitionsSmithsMedicalProFormaDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/BusinessCombinationsandAssetAcquisitionsSmithsMedicalProFormaDetails" xlink:type="extended" id="i17acee6f544c4c6da92d0871c5970e8a_BusinessCombinationsandAssetAcquisitionsSmithsMedicalProFormaDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_26ef5fb1-132b-43a8-97ed-d8ce90ea0205" 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_Revenues_300e5e5b-2055-4f55-82ef-2748cff84dfe" 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_BusinessAcquisitionLineItems_26ef5fb1-132b-43a8-97ed-d8ce90ea0205" xlink:to="loc_us-gaap_Revenues_300e5e5b-2055-4f55-82ef-2748cff84dfe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_52e7db38-a021-4201-8e73-b22353845a04" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_26ef5fb1-132b-43a8-97ed-d8ce90ea0205" xlink:to="loc_us-gaap_ProfitLoss_52e7db38-a021-4201-8e73-b22353845a04" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_628c4841-76f9-40de-b8e5-14942d0ef356" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_26ef5fb1-132b-43a8-97ed-d8ce90ea0205" xlink:to="loc_us-gaap_BusinessAcquisitionCostOfAcquiredEntityTransactionCosts_628c4841-76f9-40de-b8e5-14942d0ef356" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6aa80f80-c79f-496c-b59d-3540da78b013" 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_26ef5fb1-132b-43a8-97ed-d8ce90ea0205" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6aa80f80-c79f-496c-b59d-3540da78b013" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_1a6fbcef-e297-445f-94a1-ced977f73499" 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_6aa80f80-c79f-496c-b59d-3540da78b013" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1a6fbcef-e297-445f-94a1-ced977f73499" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1a6fbcef-e297-445f-94a1-ced977f73499_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_1a6fbcef-e297-445f-94a1-ced977f73499" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1a6fbcef-e297-445f-94a1-ced977f73499_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5eda333b-3328-4f62-81cf-97cd0dcac838" 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_1a6fbcef-e297-445f-94a1-ced977f73499" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5eda333b-3328-4f62-81cf-97cd0dcac838" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_908437ec-a481-4293-b7e5-208859ef093d" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5eda333b-3328-4f62-81cf-97cd0dcac838" xlink:to="loc_icui_SmithsMedicalMember_908437ec-a481-4293-b7e5-208859ef093d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentAxis_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonrecurringAdjustmentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6aa80f80-c79f-496c-b59d-3540da78b013" xlink:to="loc_us-gaap_NonrecurringAdjustmentAxis_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonrecurringAdjustmentDomain_ef7381c5-bc05-47d4-a277-28dba0cd44a0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonrecurringAdjustmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_NonrecurringAdjustmentAxis_d3bf10e3-01e9-49c4-afc5-e19f6b2356c1" xlink:to="loc_us-gaap_NonrecurringAdjustmentDomain_ef7381c5-bc05-47d4-a277-28dba0cd44a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AcquisitionRelatedCostsMember_01783c5c-7764-4d64-8e5e-a10b5dc426a8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AcquisitionRelatedCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NonrecurringAdjustmentDomain_ef7381c5-bc05-47d4-a277-28dba0cd44a0" xlink:to="loc_us-gaap_AcquisitionRelatedCostsMember_01783c5c-7764-4d64-8e5e-a10b5dc426a8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_2134a37c-5025-4aaf-bd39-331f309cd9aa" 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_Revenues_cb4f6edb-97c0-4b83-a862-d3daea363349" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Revenues"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_157d8cb0-6388-42af-bf74-699b577bb77d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_28d5521d-7d98-4f3a-b5fd-d03ddc4bd2cd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_7000ed9e-d229-4010-826f-16ded94108dc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7000ed9e-d229-4010-826f-16ded94108dc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1e983772-9fb0-4074-bac2-5883fb02a244" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_530f2a30-9ef7-489f-b949-284360119eb4" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationLiabilityDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#RestructuringStrategicTransactionandIntegrationLiabilityDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationLiabilityDetails" xlink:type="extended" id="ie0ea1957895149fea885a6cdee89b7e2_RestructuringStrategicTransactionandIntegrationLiabilityDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_8c1a84e3-f2df-421d-aa9d-b994d9273a45" 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_9a02cbd6-0a74-4ca2-b76c-07901053e4fb" 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_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_RestructuringReserve_9a02cbd6-0a74-4ca2-b76c-07901053e4fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_25f62d78-8fad-41a5-9a6d-14cdb4f20692" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_RestructuringCharges_25f62d78-8fad-41a5-9a6d-14cdb4f20692" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_911113b6-82a3-48be-92db-f12a654f9f2c" 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_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_PaymentsForRestructuring_911113b6-82a3-48be-92db-f12a654f9f2c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveTranslationAdjustment_a0291b0d-16e2-4832-bdd3-e9db8d6f2238" 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_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_RestructuringReserveTranslationAdjustment_a0291b0d-16e2-4832-bdd3-e9db8d6f2238" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAccrualAdjustment1_1ad903c4-7931-4865-8a6e-981453d0868a" 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_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_RestructuringReserveAccrualAdjustment1_1ad903c4-7931-4865-8a6e-981453d0868a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_414f8c54-2fb9-400a-b4fe-5d1d96118498" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestructuringReserve"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestructuringLiabilities_2f8dd12e-8800-45f0-a7d1-66142e912a18" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestructuringLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedRestructuringLiabilities_2f8dd12e-8800-45f0-a7d1-66142e912a18" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_2c4b9714-904e-491d-a11d-21ce4c78a06b" 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_8c1a84e3-f2df-421d-aa9d-b994d9273a45" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_2c4b9714-904e-491d-a11d-21ce4c78a06b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_1accaec5-193a-4a4c-b4da-7506d46675b5" 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_2c4b9714-904e-491d-a11d-21ce4c78a06b" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_1accaec5-193a-4a4c-b4da-7506d46675b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_1accaec5-193a-4a4c-b4da-7506d46675b5_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_1accaec5-193a-4a4c-b4da-7506d46675b5" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_1accaec5-193a-4a4c-b4da-7506d46675b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_d2d59ae3-3ec1-48cd-a617-e329d966d069" 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_1accaec5-193a-4a4c-b4da-7506d46675b5" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_d2d59ae3-3ec1-48cd-a617-e329d966d069" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_b0f61a4d-536e-4170-aa1f-a9b220e58385" 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_d2d59ae3-3ec1-48cd-a617-e329d966d069" xlink:to="loc_us-gaap_EmployeeSeveranceMember_b0f61a4d-536e-4170-aa1f-a9b220e58385" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FacilityClosingMember_d10b571e-4adf-4904-a779-bdff03af53d3" 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_d2d59ae3-3ec1-48cd-a617-e329d966d069" xlink:to="loc_us-gaap_FacilityClosingMember_d10b571e-4adf-4904-a779-bdff03af53d3" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#RevenueDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDetails" xlink:type="extended" id="i4c119a288f994daead4efbe4456fe53d_RevenueDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_b3d755c4-1f7b-4bed-b03a-1c5a165fc5cb" 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_RevenueRemainingPerformanceObligation_14ac58b8-b04a-4e1b-81ca-766f4af2ca89" 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_us-gaap_DisaggregationOfRevenueLineItems_b3d755c4-1f7b-4bed-b03a-1c5a165fc5cb" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_14ac58b8-b04a-4e1b-81ca-766f4af2ca89" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_12080865-c48c-434a-810c-b94aa39b7f0a" 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_b3d755c4-1f7b-4bed-b03a-1c5a165fc5cb" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_12080865-c48c-434a-810c-b94aa39b7f0a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1" 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_12080865-c48c-434a-810c-b94aa39b7f0a" xlink:to="loc_srt_ProductOrServiceAxis_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1_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_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1" xlink:to="loc_srt_ProductsAndServicesDomain_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_923fa40c-298d-4ce3-a1db-505eca2fa78b" 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_8c8bb3e5-10d0-46ff-abb7-5c3e6a1f01b1" xlink:to="loc_srt_ProductsAndServicesDomain_923fa40c-298d-4ce3-a1db-505eca2fa78b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionSystemsMember_982702b4-b9fd-4e7d-9a14-d22a44b6ed4f" xlink:href="icui-20220630.xsd#icui_InfusionSystemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_923fa40c-298d-4ce3-a1db-505eca2fa78b" xlink:to="loc_icui_InfusionSystemsMember_982702b4-b9fd-4e7d-9a14-d22a44b6ed4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_5f2dbc1c-d08b-4639-b8c1-1429a2b10945" xlink:href="icui-20220630.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_923fa40c-298d-4ce3-a1db-505eca2fa78b" xlink:to="loc_icui_EquipmentrevenueMember_5f2dbc1c-d08b-4639-b8c1-1429a2b10945" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_aeec051b-3c29-4eb8-b217-ccce8c791508" xlink:href="icui-20220630.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_923fa40c-298d-4ce3-a1db-505eca2fa78b" xlink:to="loc_icui_SoftwarerevenueMember_aeec051b-3c29-4eb8-b217-ccce8c791508" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyGeographyDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#RevenueDisaggregatedRevenuebyGeographyDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyGeographyDetails" xlink:type="extended" id="ia319f3f4b985417e9b27f48860a96c1b_RevenueDisaggregatedRevenuebyGeographyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_00f6c491-212c-4b55-8f73-a603056c5c7e" 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_74cfd13e-6b56-4a92-9bfa-f4128d4e763c" 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_00f6c491-212c-4b55-8f73-a603056c5c7e" xlink:to="loc_us-gaap_Revenues_74cfd13e-6b56-4a92-9bfa-f4128d4e763c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_f23d1282-a180-423c-b4e0-3b22f6094837" 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_00f6c491-212c-4b55-8f73-a603056c5c7e" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_f23d1282-a180-423c-b4e0-3b22f6094837" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_b7564e77-0de4-4fb6-af02-92268fe90e75" 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_f23d1282-a180-423c-b4e0-3b22f6094837" xlink:to="loc_srt_StatementGeographicalAxis_b7564e77-0de4-4fb6-af02-92268fe90e75" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_b7564e77-0de4-4fb6-af02-92268fe90e75_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_b7564e77-0de4-4fb6-af02-92268fe90e75" xlink:to="loc_srt_SegmentGeographicalDomain_b7564e77-0de4-4fb6-af02-92268fe90e75_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_ccbe9a36-fbd3-418c-8c46-909427f61ff6" 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_b7564e77-0de4-4fb6-af02-92268fe90e75" xlink:to="loc_srt_SegmentGeographicalDomain_ccbe9a36-fbd3-418c-8c46-909427f61ff6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_ef0b8a67-c827-4e67-b665-f2189e77317f" 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_ccbe9a36-fbd3-418c-8c46-909427f61ff6" xlink:to="loc_us-gaap_EMEAMember_ef0b8a67-c827-4e67-b665-f2189e77317f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherforeigncountriesMember_b2777b78-fc86-4982-9cf0-e8cb73c0524e" xlink:href="icui-20220630.xsd#icui_OtherforeigncountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ccbe9a36-fbd3-418c-8c46-909427f61ff6" xlink:to="loc_icui_OtherforeigncountriesMember_b2777b78-fc86-4982-9cf0-e8cb73c0524e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignMember_7d8e3433-288d-487e-aec8-64f48d26beb4" xlink:href="icui-20220630.xsd#icui_ForeignMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ccbe9a36-fbd3-418c-8c46-909427f61ff6" xlink:to="loc_icui_ForeignMember_7d8e3433-288d-487e-aec8-64f48d26beb4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_52cc0fe6-ea29-4399-ae61-51f5d9c82f18" 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_ccbe9a36-fbd3-418c-8c46-909427f61ff6" xlink:to="loc_country_US_52cc0fe6-ea29-4399-ae61-51f5d9c82f18" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyProductLineDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#RevenueDisaggregatedRevenuebyProductLineDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyProductLineDetails" xlink:type="extended" id="i3072cb3c243e4ba88313d18e83f03b81_RevenueDisaggregatedRevenuebyProductLineDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_bb9c241f-21d8-4e75-abcb-cb5f36541d25" 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_eb40572d-3ebc-4d34-806c-cb790ce942ee" 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_bb9c241f-21d8-4e75-abcb-cb5f36541d25" xlink:to="loc_us-gaap_Revenues_eb40572d-3ebc-4d34-806c-cb790ce942ee" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_55b5c72f-eed2-4f20-90eb-5e8213ff1048" 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_bb9c241f-21d8-4e75-abcb-cb5f36541d25" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_55b5c72f-eed2-4f20-90eb-5e8213ff1048" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_e8446bc5-cb53-4960-a1e3-347fb03caa9b" 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_55b5c72f-eed2-4f20-90eb-5e8213ff1048" xlink:to="loc_srt_ProductOrServiceAxis_e8446bc5-cb53-4960-a1e3-347fb03caa9b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e8446bc5-cb53-4960-a1e3-347fb03caa9b_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_e8446bc5-cb53-4960-a1e3-347fb03caa9b" xlink:to="loc_srt_ProductsAndServicesDomain_e8446bc5-cb53-4960-a1e3-347fb03caa9b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" 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_e8446bc5-cb53-4960-a1e3-347fb03caa9b" xlink:to="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionConsumablesMember_cfd440a3-98f2-4f0a-8b9a-aed639f2f013" xlink:href="icui-20220630.xsd#icui_InfusionConsumablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_InfusionConsumablesMember_cfd440a3-98f2-4f0a-8b9a-aed639f2f013" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionSystemsMember_c0d4b13a-04d0-429e-b2fe-32d8c69f7392" xlink:href="icui-20220630.xsd#icui_InfusionSystemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_InfusionSystemsMember_c0d4b13a-04d0-429e-b2fe-32d8c69f7392" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IVSolutionsMember_3f1c1c4b-84cc-49bb-8ea8-193210b88b3f" xlink:href="icui-20220630.xsd#icui_IVSolutionsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_IVSolutionsMember_3f1c1c4b-84cc-49bb-8ea8-193210b88b3f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CriticalCareMember_013877ed-4284-4986-bc67-e7bc4001d2e9" xlink:href="icui-20220630.xsd#icui_CriticalCareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_CriticalCareMember_013877ed-4284-4986-bc67-e7bc4001d2e9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionConsumablesSmithsMedicalMember_b25a03eb-4ee6-4947-9462-dce8f5561ff5" xlink:href="icui-20220630.xsd#icui_InfusionConsumablesSmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_InfusionConsumablesSmithsMedicalMember_b25a03eb-4ee6-4947-9462-dce8f5561ff5" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_VascularAccessMember_aa524075-1f8d-4327-9269-3563ccc272c3" xlink:href="icui-20220630.xsd#icui_VascularAccessMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_VascularAccessMember_aa524075-1f8d-4327-9269-3563ccc272c3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_VitalCareMember_fad90faf-45bd-45e8-8258-5cab3b7fd569" xlink:href="icui-20220630.xsd#icui_VitalCareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_0d7c3cf1-a035-4b1b-ba7c-36a3eedb4563" xlink:to="loc_icui_VitalCareMember_fad90faf-45bd-45e8-8258-5cab3b7fd569" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#RevenueContractLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="extended" id="ia311728dc6b449c9bcbfce0a8a4ece76_RevenueContractLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:href="icui-20220630.xsd#icui_ContractassetandliabilitybalancesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInDeferredRevenueRollForward_e3be2bf7-ab0a-4bf8-ae5b-3139366ef1f2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MovementInDeferredRevenueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_us-gaap_MovementInDeferredRevenueRollForward_e3be2bf7-ab0a-4bf8-ae5b-3139366ef1f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_7dc18ce7-2f54-4241-978a-f10c3c674d2a" 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_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_us-gaap_ContractWithCustomerLiability_7dc18ce7-2f54-4241-978a-f10c3c674d2a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_2dc04c48-c5f3-4be2-82c3-2e9203fbc92a" 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_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_2dc04c48-c5f3-4be2-82c3-2e9203fbc92a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueAdditions_38edb890-978f-4792-b98f-82cad2b87a81" 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_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_us-gaap_DeferredRevenueAdditions_38edb890-978f-4792-b98f-82cad2b87a81" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_31283669-c0c5-443d-b1b1-5505b31da2bb" 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_us-gaap_RevenueRemainingPerformanceObligation_98213d09-9ef5-4b16-b8a7-94a03d8b57e7" 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_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_98213d09-9ef5-4b16-b8a7-94a03d8b57e7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesTable_ce0c05a2-b94a-413f-90a4-f8380ca24873" xlink:href="icui-20220630.xsd#icui_ContractassetandliabilitybalancesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_f9137b00-2541-4636-a4c2-4c10ba1091a1" xlink:to="loc_icui_ContractassetandliabilitybalancesTable_ce0c05a2-b94a-413f-90a4-f8380ca24873" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_7255e9c1-0d3c-40ee-a815-cf74c7cec691" 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_ce0c05a2-b94a-413f-90a4-f8380ca24873" xlink:to="loc_srt_ProductOrServiceAxis_7255e9c1-0d3c-40ee-a815-cf74c7cec691" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_7255e9c1-0d3c-40ee-a815-cf74c7cec691_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_7255e9c1-0d3c-40ee-a815-cf74c7cec691" xlink:to="loc_srt_ProductsAndServicesDomain_7255e9c1-0d3c-40ee-a815-cf74c7cec691_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" 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_7255e9c1-0d3c-40ee-a815-cf74c7cec691" xlink:to="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_18b887fc-b075-40a5-8aa9-9161393e4da5" xlink:href="icui-20220630.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" xlink:to="loc_icui_EquipmentrevenueMember_18b887fc-b075-40a5-8aa9-9161393e4da5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_298a97a4-2b91-45fd-b73f-db1c4bc5607c" xlink:href="icui-20220630.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" xlink:to="loc_icui_SoftwarerevenueMember_298a97a4-2b91-45fd-b73f-db1c4bc5607c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GovernmentGrantRevenueMember_4d4ebd12-9ff5-4cba-a61d-ea41db8942c8" xlink:href="icui-20220630.xsd#icui_GovernmentGrantRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" xlink:to="loc_icui_GovernmentGrantRevenueMember_4d4ebd12-9ff5-4cba-a61d-ea41db8942c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherDeferredRevenueMember_14221855-7951-48fd-a950-93c1a97f72dd" xlink:href="icui-20220630.xsd#icui_OtherDeferredRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_e0cadbe8-88bb-4b06-90d6-3dfd101e2015" xlink:to="loc_icui_OtherDeferredRevenueMember_14221855-7951-48fd-a950-93c1a97f72dd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_98a66f02-0063-437b-a695-6fc9f6480530" 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_icui_ContractassetandliabilitybalancesTable_ce0c05a2-b94a-413f-90a4-f8380ca24873" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_98a66f02-0063-437b-a695-6fc9f6480530" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_98a66f02-0063-437b-a695-6fc9f6480530_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_98a66f02-0063-437b-a695-6fc9f6480530" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_98a66f02-0063-437b-a695-6fc9f6480530_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81ab58ee-434d-41cb-b399-5cc518e6ebf9" 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_98a66f02-0063-437b-a695-6fc9f6480530" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81ab58ee-434d-41cb-b399-5cc518e6ebf9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_2ebfd83e-b314-445b-b329-a0dfd41e0d95" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_81ab58ee-434d-41cb-b399-5cc518e6ebf9" xlink:to="loc_icui_SmithsMedicalMember_2ebfd83e-b314-445b-b329-a0dfd41e0d95" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_1b35f211-ef58-460b-9c5b-c07271e1430a" xlink:href="icui-20220630.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ContractassetandliabilitybalancesTable_ce0c05a2-b94a-413f-90a4-f8380ca24873" xlink:to="loc_icui_TimingAxis_1b35f211-ef58-460b-9c5b-c07271e1430a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_1b35f211-ef58-460b-9c5b-c07271e1430a_default" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_1b35f211-ef58-460b-9c5b-c07271e1430a" xlink:to="loc_icui_TimingDomain_1b35f211-ef58-460b-9c5b-c07271e1430a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_f4117485-5e2f-4afa-aa3a-c38f44138c28" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_1b35f211-ef58-460b-9c5b-c07271e1430a" xlink:to="loc_icui_TimingDomain_f4117485-5e2f-4afa-aa3a-c38f44138c28" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermMember_de069813-1018-4899-a504-fd34ee0ae8b3" xlink:href="icui-20220630.xsd#icui_ShortTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_f4117485-5e2f-4afa-aa3a-c38f44138c28" xlink:to="loc_icui_ShortTermMember_de069813-1018-4899-a504-fd34ee0ae8b3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermMember_3fe2decf-85af-47f7-8f8c-4194109dea6f" xlink:href="icui-20220630.xsd#icui_LongTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_f4117485-5e2f-4afa-aa3a-c38f44138c28" xlink:to="loc_icui_LongTermMember_3fe2decf-85af-47f7-8f8c-4194109dea6f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesTextDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#LeasesTextDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesTextDetails" xlink:type="extended" id="ic56de892f8a24792a35f414950421de6_LeasesTextDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_7d8dfa0b-e437-41f9-8961-7cbb9dc1b0cf" 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_35e9d0d9-e778-402a-9879-625cd0f5477d" xlink:href="icui-20220630.xsd#icui_Optiontoextendinyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_7d8dfa0b-e437-41f9-8961-7cbb9dc1b0cf" xlink:to="loc_icui_Optiontoextendinyears_35e9d0d9-e778-402a-9879-625cd0f5477d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_ed96ca93-9327-4eaa-a7d0-ed60bf520923" 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_7d8dfa0b-e437-41f9-8961-7cbb9dc1b0cf" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_ed96ca93-9327-4eaa-a7d0-ed60bf520923" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_c00b6d49-90d5-481a-a34c-66a935629937" 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_7d8dfa0b-e437-41f9-8961-7cbb9dc1b0cf" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_c00b6d49-90d5-481a-a34c-66a935629937" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2" 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_c00b6d49-90d5-481a-a34c-66a935629937" xlink:to="loc_srt_RangeAxis_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2_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_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2" xlink:to="loc_srt_RangeMember_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_fd72ff22-545c-46dc-9ffe-fde59355351b" 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_e0db06e9-6193-4b5c-8c59-2150cb7cd3b2" xlink:to="loc_srt_RangeMember_fd72ff22-545c-46dc-9ffe-fde59355351b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_9fff9dde-5ceb-4fae-8b2b-fd4cc7c15571" 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_fd72ff22-545c-46dc-9ffe-fde59355351b" xlink:to="loc_srt_MaximumMember_9fff9dde-5ceb-4fae-8b2b-fd4cc7c15571" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_74864462-cd7c-4862-ad27-de118e21f863" 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_fd72ff22-545c-46dc-9ffe-fde59355351b" xlink:to="loc_srt_MinimumMember_74864462-cd7c-4862-ad27-de118e21f863" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/NetIncomePerShareDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#NetIncomePerShareDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/NetIncomePerShareDetails" xlink:type="extended" id="i9ecba423e3424adca3cd77819e0098ef_NetIncomePerShareDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91592a0-1b17-47ea-b6d1-d01fa6564c42" 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_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_18a4ebfc-bf4c-44b7-b9e8-87ec117ac1cf" 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_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_18a4ebfc-bf4c-44b7-b9e8-87ec117ac1cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_16180e04-e080-40b3-9785-9baf0ece21ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_ProfitLoss_16180e04-e080-40b3-9785-9baf0ece21ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_667b57fe-9ba6-4f95-9a77-4e64770269cc" 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_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_667b57fe-9ba6-4f95-9a77-4e64770269cc" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_493284af-ef4c-4f3a-9308-66e7b453d803" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_493284af-ef4c-4f3a-9308-66e7b453d803" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_f8084b28-407b-485d-9681-34112694d4d1" 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_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_f8084b28-407b-485d-9681-34112694d4d1" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_74271e03-16fe-4df6-ae72-67668af04074" 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_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_EarningsPerShareBasic_74271e03-16fe-4df6-ae72-67668af04074" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_6da81129-cd4d-487d-862f-5512cc4277a5" 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_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_EarningsPerShareDiluted_6da81129-cd4d-487d-862f-5512cc4277a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_2b72e5f7-9f4c-4a3b-a49f-2e2e3279016b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_f91592a0-1b17-47ea-b6d1-d01fa6564c42" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_2b72e5f7-9f4c-4a3b-a49f-2e2e3279016b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2" 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_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_2b72e5f7-9f4c-4a3b-a49f-2e2e3279016b" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2_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_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8ef38bb0-92e2-4866-8572-fa8969d36982" 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_ca8b790b-3a4f-4fe9-afe6-2e740b7e71e2" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_8ef38bb0-92e2-4866-8572-fa8969d36982" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails" xlink:type="extended" id="i7c221aeaf03f4c909887c36ecc9e24ee_DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_e533d961-c90f-4b60-a992-87faaa4a4ab4" 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_DerivativeNotionalAmount_560190e2-8d47-4736-81dd-5daa92aa28f2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_e533d961-c90f-4b60-a992-87faaa4a4ab4" xlink:to="loc_us-gaap_DerivativeNotionalAmount_560190e2-8d47-4736-81dd-5daa92aa28f2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_fa0519dc-e4d3-4679-af9e-3a3558cf077e" 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_e533d961-c90f-4b60-a992-87faaa4a4ab4" xlink:to="loc_us-gaap_DerivativeTable_fa0519dc-e4d3-4679-af9e-3a3558cf077e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_61b78cf2-fda4-402c-8eb5-6bfb5f365a77" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_fa0519dc-e4d3-4679-af9e-3a3558cf077e" xlink:to="loc_srt_CurrencyAxis_61b78cf2-fda4-402c-8eb5-6bfb5f365a77" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_61b78cf2-fda4-402c-8eb5-6bfb5f365a77_default" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_61b78cf2-fda4-402c-8eb5-6bfb5f365a77" xlink:to="loc_currency_AllCurrenciesDomain_61b78cf2-fda4-402c-8eb5-6bfb5f365a77_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_61b78cf2-fda4-402c-8eb5-6bfb5f365a77" xlink:to="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_MXN_e447d763-c700-4698-adf9-faf63952a8b7" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_MXN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:to="loc_currency_MXN_e447d763-c700-4698-adf9-faf63952a8b7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_EUR_e69417a1-cf33-4e3b-a01b-89f61279b665" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_EUR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:to="loc_currency_EUR_e69417a1-cf33-4e3b-a01b-89f61279b665" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_CZK_32c4a0eb-e51b-4678-8f14-6c0b37755df7" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_CZK"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:to="loc_currency_CZK_32c4a0eb-e51b-4678-8f14-6c0b37755df7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_JPY_b51ac00d-e956-4a9a-a2cf-cf4c4a4cc945" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_JPY"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_98c5ebb1-1d72-49bd-8942-51a829d2a5ae" xlink:to="loc_currency_JPY_b51ac00d-e956-4a9a-a2cf-cf4c4a4cc945" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisAxis_2502d45f-a2a7-426c-8b77-ce72493700fe" xlink:href="icui-20220630.xsd#icui_Srt_MultipleCurrencyAxisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_fa0519dc-e4d3-4679-af9e-3a3558cf077e" xlink:to="loc_icui_Srt_MultipleCurrencyAxisAxis_2502d45f-a2a7-426c-8b77-ce72493700fe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisDomain_2502d45f-a2a7-426c-8b77-ce72493700fe_default" xlink:href="icui-20220630.xsd#icui_Srt_MultipleCurrencyAxisDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_Srt_MultipleCurrencyAxisAxis_2502d45f-a2a7-426c-8b77-ce72493700fe" xlink:to="loc_icui_Srt_MultipleCurrencyAxisDomain_2502d45f-a2a7-426c-8b77-ce72493700fe_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisDomain_19e742c0-e427-45a7-9288-8d350788f4ba" xlink:href="icui-20220630.xsd#icui_Srt_MultipleCurrencyAxisDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_Srt_MultipleCurrencyAxisAxis_2502d45f-a2a7-426c-8b77-ce72493700fe" xlink:to="loc_icui_Srt_MultipleCurrencyAxisDomain_19e742c0-e427-45a7-9288-8d350788f4ba" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherCurrenciesMember_5fd08226-5d80-458c-b1aa-2e30ead34f59" xlink:href="icui-20220630.xsd#icui_OtherCurrenciesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_Srt_MultipleCurrencyAxisDomain_19e742c0-e427-45a7-9288-8d350788f4ba" xlink:to="loc_icui_OtherCurrenciesMember_5fd08226-5d80-458c-b1aa-2e30ead34f59" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDetails" xlink:type="extended" id="i668ee67c0a9f451da23ff4fe85bab75c_DerivativeFinancialInstrumentsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_98ffcb48-57df-433f-89ed-ec8401967427" 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_90d88060-e7cd-48cd-a0c9-af0292c34d98" 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_98ffcb48-57df-433f-89ed-ec8401967427" xlink:to="loc_us-gaap_DerivativeForwardExchangeRate1_90d88060-e7cd-48cd-a0c9-af0292c34d98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNotionalAmount_0f296163-af2d-4caf-ae55-d9086fff35e8" 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_98ffcb48-57df-433f-89ed-ec8401967427" xlink:to="loc_us-gaap_DerivativeAssetNotionalAmount_0f296163-af2d-4caf-ae55-d9086fff35e8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_04d9eff6-2414-405d-80a9-a4328300b39d" 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_98ffcb48-57df-433f-89ed-ec8401967427" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_04d9eff6-2414-405d-80a9-a4328300b39d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_a1eb5234-67b4-4dfe-a29a-b446ddd0a41c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_98ffcb48-57df-433f-89ed-ec8401967427" xlink:to="loc_us-gaap_DerivativeNotionalAmount_a1eb5234-67b4-4dfe-a29a-b446ddd0a41c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_11cab3eb-b77c-402d-a1d9-e74f8e0ff427" 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_98ffcb48-57df-433f-89ed-ec8401967427" xlink:to="loc_us-gaap_DerivativeTable_11cab3eb-b77c-402d-a1d9-e74f8e0ff427" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5" 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_11cab3eb-b77c-402d-a1d9-e74f8e0ff427" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5_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_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_156f45c5-7203-4be9-a861-8f1f3d4f3c30" 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_3bcfa680-b32d-40bc-b19b-5013bcfc3ed5" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_156f45c5-7203-4be9-a861-8f1f3d4f3c30" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge2Member_b091dd57-0c99-4dcd-8825-575e1307bddf" xlink:href="icui-20220630.xsd#icui_Hedge2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_156f45c5-7203-4be9-a861-8f1f3d4f3c30" xlink:to="loc_icui_Hedge2Member_b091dd57-0c99-4dcd-8825-575e1307bddf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Hedge3MemberMember_2607b3d1-49e1-45f7-9674-abe4a00ef79d" xlink:href="icui-20220630.xsd#icui_Hedge3MemberMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_156f45c5-7203-4be9-a861-8f1f3d4f3c30" xlink:to="loc_icui_Hedge3MemberMember_2607b3d1-49e1-45f7-9674-abe4a00ef79d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_937e2ba4-9650-4e31-a17f-5997500ee231" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_11cab3eb-b77c-402d-a1d9-e74f8e0ff427" xlink:to="loc_srt_CurrencyAxis_937e2ba4-9650-4e31-a17f-5997500ee231" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_937e2ba4-9650-4e31-a17f-5997500ee231_default" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_937e2ba4-9650-4e31-a17f-5997500ee231" xlink:to="loc_currency_AllCurrenciesDomain_937e2ba4-9650-4e31-a17f-5997500ee231_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_e4787339-1995-4c28-9d79-c2eb7fbcc94e" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_937e2ba4-9650-4e31-a17f-5997500ee231" xlink:to="loc_currency_AllCurrenciesDomain_e4787339-1995-4c28-9d79-c2eb7fbcc94e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_MXN_b0dbc487-d872-416a-9940-c248ee01b56d" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_MXN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_e4787339-1995-4c28-9d79-c2eb7fbcc94e" xlink:to="loc_currency_MXN_b0dbc487-d872-416a-9940-c248ee01b56d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_CNY_a09439c1-9dd1-46f5-adc6-09aeed2b4f31" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_CNY"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_e4787339-1995-4c28-9d79-c2eb7fbcc94e" xlink:to="loc_currency_CNY_a09439c1-9dd1-46f5-adc6-09aeed2b4f31" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_USD_64a2d4b2-ad32-45f9-a7f0-fda9db5542b7" xlink:href="https://xbrl.sec.gov/currency/2021/currency-2021.xsd#currency_USD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_e4787339-1995-4c28-9d79-c2eb7fbcc94e" xlink:to="loc_currency_USD_64a2d4b2-ad32-45f9-a7f0-fda9db5542b7" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsInterestRateSwapsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsInterestRateSwapsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsInterestRateSwapsDetails" xlink:type="extended" id="i7459e99c71984a19ae243777d4ec7266_DerivativeFinancialInstrumentsInterestRateSwapsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_7abffde0-fc3b-425d-b29c-2793b26c3e16" 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_DerivativeNotionalAmount_9fd2fa9b-fc86-4ae7-84ad-1623ad949acf" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_7abffde0-fc3b-425d-b29c-2793b26c3e16" xlink:to="loc_us-gaap_DerivativeNotionalAmount_9fd2fa9b-fc86-4ae7-84ad-1623ad949acf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InterestRateSwapEndingNotionalValue_53fdcdda-7f04-409b-a5fb-231b0aaa8e53" xlink:href="icui-20220630.xsd#icui_InterestRateSwapEndingNotionalValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_7abffde0-fc3b-425d-b29c-2793b26c3e16" xlink:to="loc_icui_InterestRateSwapEndingNotionalValue_53fdcdda-7f04-409b-a5fb-231b0aaa8e53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_dc7f4366-7756-4ee5-9497-0d8a1f017271" 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_7abffde0-fc3b-425d-b29c-2793b26c3e16" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_dc7f4366-7756-4ee5-9497-0d8a1f017271" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_DerivativeVariableRateFloor_8fa65635-62ce-449e-838c-01ac0f806051" xlink:href="icui-20220630.xsd#icui_DerivativeVariableRateFloor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_7abffde0-fc3b-425d-b29c-2793b26c3e16" xlink:to="loc_icui_DerivativeVariableRateFloor_8fa65635-62ce-449e-838c-01ac0f806051" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_a3cde0e2-6162-42a1-8124-c3de23707eaa" 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_7abffde0-fc3b-425d-b29c-2793b26c3e16" xlink:to="loc_us-gaap_DerivativeTable_a3cde0e2-6162-42a1-8124-c3de23707eaa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_f93212f4-7984-4eb5-826b-0447995e8d2b" 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_a3cde0e2-6162-42a1-8124-c3de23707eaa" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_f93212f4-7984-4eb5-826b-0447995e8d2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_f93212f4-7984-4eb5-826b-0447995e8d2b_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_f93212f4-7984-4eb5-826b-0447995e8d2b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_f93212f4-7984-4eb5-826b-0447995e8d2b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c25ec7b5-aad8-49f2-ab29-c0ff41f337dd" 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_f93212f4-7984-4eb5-826b-0447995e8d2b" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c25ec7b5-aad8-49f2-ab29-c0ff41f337dd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_77e616f7-f7fb-4d66-8892-c3fb7c39fdfd" 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_c25ec7b5-aad8-49f2-ab29-c0ff41f337dd" xlink:to="loc_us-gaap_InterestRateSwapMember_77e616f7-f7fb-4d66-8892-c3fb7c39fdfd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_5db057a1-978c-4f01-a9ac-c56fac906135" xlink:href="icui-20220630.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_a3cde0e2-6162-42a1-8124-c3de23707eaa" xlink:to="loc_icui_TermLoanAxis_5db057a1-978c-4f01-a9ac-c56fac906135" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_5db057a1-978c-4f01-a9ac-c56fac906135_default" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_5db057a1-978c-4f01-a9ac-c56fac906135" xlink:to="loc_icui_TermLoanDomain_5db057a1-978c-4f01-a9ac-c56fac906135_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_5f408903-6617-46d2-924a-24155bcbc651" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_5db057a1-978c-4f01-a9ac-c56fac906135" xlink:to="loc_icui_TermLoanDomain_5f408903-6617-46d2-924a-24155bcbc651" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_d4b19d3b-b85a-438d-b66b-02a25c459866" xlink:href="icui-20220630.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_5f408903-6617-46d2-924a-24155bcbc651" xlink:to="loc_icui_TermLoanAMember_d4b19d3b-b85a-438d-b66b-02a25c459866" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_352f0e6f-1155-470d-a8c0-93767bcca759" xlink:href="icui-20220630.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_5f408903-6617-46d2-924a-24155bcbc651" xlink:to="loc_icui_TermLoanBMember_352f0e6f-1155-470d-a8c0-93767bcca759" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="extended" id="i78d9b315e0544133b88254e0c1d88599_DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_ef5126b5-d188-4800-a745-ede7b518abe4" 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_82303b03-5319-4fe7-b4dc-c92f8fb0e38d" 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_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeAssets_82303b03-5319-4fe7-b4dc-c92f8fb0e38d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_d8cce746-5501-42f7-9783-b2300122e226" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_d8cce746-5501-42f7-9783-b2300122e226" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_fe13be09-fd3a-42ac-8d81-d70e6c9acaee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_fe13be09-fd3a-42ac-8d81-d70e6c9acaee" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_de89a182-31af-4732-9ce5-16287208ef02" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_de89a182-31af-4732-9ce5-16287208ef02" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesNoncurrent_d9b0d769-d70c-4294-b46b-bd3b3c4b6673" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_d9b0d769-d70c-4294-b46b-bd3b3c4b6673" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_4a5bc46c-2645-4051-b6d4-d73700aba068" 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_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_DerivativeLiabilities_4a5bc46c-2645-4051-b6d4-d73700aba068" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_d60c7623-0be0-48bd-a514-6d0b32455af5" 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_ef5126b5-d188-4800-a745-ede7b518abe4" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_d60c7623-0be0-48bd-a514-6d0b32455af5" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_b4faad45-3d5f-43ab-b4c4-c62c70e81123" 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_d60c7623-0be0-48bd-a514-6d0b32455af5" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_b4faad45-3d5f-43ab-b4c4-c62c70e81123" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b4faad45-3d5f-43ab-b4c4-c62c70e81123_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_b4faad45-3d5f-43ab-b4c4-c62c70e81123" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b4faad45-3d5f-43ab-b4c4-c62c70e81123_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_7b7eb75e-3497-4cb4-b523-75d98c00d1b9" 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_b4faad45-3d5f-43ab-b4c4-c62c70e81123" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_7b7eb75e-3497-4cb4-b523-75d98c00d1b9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_5ae62477-2163-4e06-bb96-54234d111934" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_7b7eb75e-3497-4cb4-b523-75d98c00d1b9" xlink:to="loc_us-gaap_ForeignExchangeContractMember_5ae62477-2163-4e06-bb96-54234d111934" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_ab785f80-a106-473a-9dc2-75f5f479a0da" 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_7b7eb75e-3497-4cb4-b523-75d98c00d1b9" xlink:to="loc_us-gaap_InterestRateSwapMember_ab785f80-a106-473a-9dc2-75f5f479a0da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_7260fdc8-4f97-44cf-bde8-efc45997c05e" 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_d60c7623-0be0-48bd-a514-6d0b32455af5" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_7260fdc8-4f97-44cf-bde8-efc45997c05e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_7260fdc8-4f97-44cf-bde8-efc45997c05e_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_7260fdc8-4f97-44cf-bde8-efc45997c05e" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_7260fdc8-4f97-44cf-bde8-efc45997c05e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_19f47772-f426-42b8-802b-4c80df340757" 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_7260fdc8-4f97-44cf-bde8-efc45997c05e" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_19f47772-f426-42b8-802b-4c80df340757" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_27c7b656-bbcc-4f73-9c3d-3de107ea630f" 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_19f47772-f426-42b8-802b-4c80df340757" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_27c7b656-bbcc-4f73-9c3d-3de107ea630f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_569386a5-88f3-4258-8017-c5caa560853a" 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_19f47772-f426-42b8-802b-4c80df340757" xlink:to="loc_us-gaap_OtherAssetsMember_569386a5-88f3-4258-8017-c5caa560853a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_c952109e-369a-4c87-b49a-bec314bb4eef" 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_19f47772-f426-42b8-802b-4c80df340757" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_c952109e-369a-4c87-b49a-bec314bb4eef" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesMember_ce740da3-bb38-4d47-b657-3d5a0ca4ac3c" 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_19f47772-f426-42b8-802b-4c80df340757" xlink:to="loc_us-gaap_OtherLiabilitiesMember_ce740da3-bb38-4d47-b657-3d5a0ca4ac3c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b7226c09-3305-45e7-b0c5-039dcc027557" 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_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_d60c7623-0be0-48bd-a514-6d0b32455af5" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_b7226c09-3305-45e7-b0c5-039dcc027557" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_b7226c09-3305-45e7-b0c5-039dcc027557_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_b7226c09-3305-45e7-b0c5-039dcc027557" xlink:to="loc_us-gaap_HedgingRelationshipDomain_b7226c09-3305-45e7-b0c5-039dcc027557_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_2e69f9e1-9aa3-4b69-bd5c-7d2088ec564b" 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_b7226c09-3305-45e7-b0c5-039dcc027557" xlink:to="loc_us-gaap_HedgingRelationshipDomain_2e69f9e1-9aa3-4b69-bd5c-7d2088ec564b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended" id="ie37809ec1a1b43b49db5211811e16fa9_DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_189caa7b-d50d-4a54-bc79-edebbc550d94" 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_OtherComprehensiveIncomeLossBeforeTax_a42e4e31-cc4b-465d-8073-82cc65dcec63" 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_189caa7b-d50d-4a54-bc79-edebbc550d94" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_a42e4e31-cc4b-465d-8073-82cc65dcec63" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_a0c86202-560d-4069-a341-8474932056d8" 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_189caa7b-d50d-4a54-bc79-edebbc550d94" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_a0c86202-560d-4069-a341-8474932056d8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_9a069e93-14ba-4268-8270-a757b874db23" 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_a0c86202-560d-4069-a341-8474932056d8" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_9a069e93-14ba-4268-8270-a757b874db23" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9a069e93-14ba-4268-8270-a757b874db23_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_9a069e93-14ba-4268-8270-a757b874db23" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9a069e93-14ba-4268-8270-a757b874db23_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_a9e90dfc-994d-487f-9829-50db5a59a104" 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_9a069e93-14ba-4268-8270-a757b874db23" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_a9e90dfc-994d-487f-9829-50db5a59a104" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_205e240b-efa3-42ee-8404-ea1e433cdbc6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_a9e90dfc-994d-487f-9829-50db5a59a104" xlink:to="loc_us-gaap_ForeignExchangeContractMember_205e240b-efa3-42ee-8404-ea1e433cdbc6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_17ebc37b-54d9-4b94-a64e-32f477a2c17b" 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_a9e90dfc-994d-487f-9829-50db5a59a104" xlink:to="loc_us-gaap_InterestRateSwapMember_17ebc37b-54d9-4b94-a64e-32f477a2c17b" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails" xlink:type="extended" id="i7c7200c0d3c146049d2592fe7a0c5eea_DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_f6e7a621-72a6-475f-ae5b-946696ad6592" 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_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_f6e7a621-72a6-475f-ae5b-946696ad6592" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_0467de5b-92e6-4edf-9216-b83488bda726" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_DerivativeInstrumentsLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_0467de5b-92e6-4edf-9216-b83488bda726" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_5def0355-2acc-4aa5-bb7d-f9d21addc882" 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_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_5def0355-2acc-4aa5-bb7d-f9d21addc882" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_48886faa-5fda-47aa-8b11-f9870f1f8b78" 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_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_48886faa-5fda-47aa-8b11-f9870f1f8b78" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet_d4901ad2-fae5-4b6c-873c-9f11be89a3ba" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet_d4901ad2-fae5-4b6c-873c-9f11be89a3ba" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_a332ffd8-577d-4c4e-a736-5f819e1ce981" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_f8283c17-71bc-49ff-a993-5c010fd2b53f" 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_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_f8283c17-71bc-49ff-a993-5c010fd2b53f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_f8283c17-71bc-49ff-a993-5c010fd2b53f_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_f8283c17-71bc-49ff-a993-5c010fd2b53f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_f8283c17-71bc-49ff-a993-5c010fd2b53f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4a6fe299-c6f9-453b-a4fb-076035f88570" 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_f8283c17-71bc-49ff-a993-5c010fd2b53f" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4a6fe299-c6f9-453b-a4fb-076035f88570" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_75b1fe8d-b2b4-4548-a739-b955ef3269ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4a6fe299-c6f9-453b-a4fb-076035f88570" xlink:to="loc_us-gaap_ForeignExchangeContractMember_75b1fe8d-b2b4-4548-a739-b955ef3269ae" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_8dea3de1-e74a-4efa-aec6-cd46e05250a9" 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_4a6fe299-c6f9-453b-a4fb-076035f88570" xlink:to="loc_us-gaap_InterestRateSwapMember_8dea3de1-e74a-4efa-aec6-cd46e05250a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a" 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_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a_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_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_f274fc2b-30c6-432b-a052-e74259f69218" 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_489a8ad6-b6e9-48ca-b5ab-c563a0b9d35a" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_f274fc2b-30c6-432b-a052-e74259f69218" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingRevenueMember_1df77f23-cc05-4988-8f68-4abad68d55b2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TradingRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f274fc2b-30c6-432b-a052-e74259f69218" xlink:to="loc_us-gaap_TradingRevenueMember_1df77f23-cc05-4988-8f68-4abad68d55b2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_7867af4d-3099-405c-935a-e4d275895edc" 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_f274fc2b-30c6-432b-a052-e74259f69218" xlink:to="loc_us-gaap_CostOfSalesMember_7867af4d-3099-405c-935a-e4d275895edc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseMember_ea400e55-a7ba-49fc-be6c-b149dc9f2975" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_f274fc2b-30c6-432b-a052-e74259f69218" xlink:to="loc_us-gaap_InterestExpenseMember_ea400e55-a7ba-49fc-be6c-b149dc9f2975" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationAxis_f9618053-0115-4a16-bc65-3551ac42843b" 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_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:to="loc_us-gaap_HedgingDesignationAxis_f9618053-0115-4a16-bc65-3551ac42843b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_f9618053-0115-4a16-bc65-3551ac42843b_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_f9618053-0115-4a16-bc65-3551ac42843b" xlink:to="loc_us-gaap_HedgingDesignationDomain_f9618053-0115-4a16-bc65-3551ac42843b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingDesignationDomain_eca8273d-6005-4ed8-a065-b0debcb0f850" 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_f9618053-0115-4a16-bc65-3551ac42843b" xlink:to="loc_us-gaap_HedgingDesignationDomain_eca8273d-6005-4ed8-a065-b0debcb0f850" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_3e01483f-6464-417a-bf06-0cc837e67fd6" 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_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_ef690c86-1a0f-4bdd-aba3-49e6d19e335d" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_3e01483f-6464-417a-bf06-0cc837e67fd6" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_3e01483f-6464-417a-bf06-0cc837e67fd6_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_3e01483f-6464-417a-bf06-0cc837e67fd6" xlink:to="loc_us-gaap_HedgingRelationshipDomain_3e01483f-6464-417a-bf06-0cc837e67fd6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_f346b1bf-4efb-4914-abea-976db1d55415" 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_3e01483f-6464-417a-bf06-0cc837e67fd6" xlink:to="loc_us-gaap_HedgingRelationshipDomain_f346b1bf-4efb-4914-abea-976db1d55415" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_9a5af5f9-d124-4188-a761-680a588a5204" 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_f346b1bf-4efb-4914-abea-976db1d55415" xlink:to="loc_us-gaap_CashFlowHedgingMember_9a5af5f9-d124-4188-a761-680a588a5204" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#FairValueMeasuresandDisclosuresDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresDetails" xlink:type="extended" id="i527b35b5ff064a0783d38c234c92e16b_FairValueMeasuresandDisclosuresDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_217f8b9f-2739-4362-94ce-65c064fce2a4" xlink:href="icui-20220630.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_icui_Contingentconsiderationgross_217f8b9f-2739-4362-94ce-65c064fce2a4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_f6d54a11-6ccf-42b1-b6b8-0d454657c810" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_f6d54a11-6ccf-42b1-b6b8-0d454657c810" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossST_c27ceb4d-c302-4082-8644-1d9693ef3896" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossST"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_icui_ContingentConsiderationGrossST_c27ceb4d-c302-4082-8644-1d9693ef3896" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossLT_bc2a4a75-0e12-430b-bc90-f6ef4f66766c" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossLT"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_icui_ContingentConsiderationGrossLT_bc2a4a75-0e12-430b-bc90-f6ef4f66766c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_074f98b3-454d-40a4-8983-c20628b6e946" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_074f98b3-454d-40a4-8983-c20628b6e946" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OwnershipRequirementForEarnoutPayment_069c030e-f0b3-4acd-970e-dd21515d3a08" xlink:href="icui-20220630.xsd#icui_OwnershipRequirementForEarnoutPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_icui_OwnershipRequirementForEarnoutPayment_069c030e-f0b3-4acd-970e-dd21515d3a08" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_96565c84-62da-4d57-9c78-c8e2b1eb56a3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1748e0e5-788c-4e97-9025-92124a1e52ae" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_96565c84-62da-4d57-9c78-c8e2b1eb56a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_5cd976f5-cdbd-4575-a6c8-30296b1e4bae" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_96565c84-62da-4d57-9c78-c8e2b1eb56a3" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_5cd976f5-cdbd-4575-a6c8-30296b1e4bae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5cd976f5-cdbd-4575-a6c8-30296b1e4bae_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_5cd976f5-cdbd-4575-a6c8-30296b1e4bae" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5cd976f5-cdbd-4575-a6c8-30296b1e4bae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_545bd036-e70e-4cf7-9549-07e8f5168b64" 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_5cd976f5-cdbd-4575-a6c8-30296b1e4bae" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_545bd036-e70e-4cf7-9549-07e8f5168b64" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_a309dbb2-9009-4ed5-b94e-2d6c8bead724" xlink:href="icui-20220630.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_545bd036-e70e-4cf7-9549-07e8f5168b64" xlink:to="loc_icui_PursuitVascularInc.Member_a309dbb2-9009-4ed5-b94e-2d6c8bead724" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_75859d0f-540a-4bf6-8a65-a12282a8d1fb" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_545bd036-e70e-4cf7-9549-07e8f5168b64" xlink:to="loc_icui_SmithsMedicalMember_75859d0f-540a-4bf6-8a65-a12282a8d1fb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_6cc6774d-fb97-4653-aec5-dbe675c9ba3c" xlink:href="icui-20220630.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_545bd036-e70e-4cf7-9549-07e8f5168b64" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_6cc6774d-fb97-4653-aec5-dbe675c9ba3c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_77734049-f52d-4e5c-b6e5-557f00db9af3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContingentConsiderationByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_96565c84-62da-4d57-9c78-c8e2b1eb56a3" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_77734049-f52d-4e5c-b6e5-557f00db9af3" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_77734049-f52d-4e5c-b6e5-557f00db9af3_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_77734049-f52d-4e5c-b6e5-557f00db9af3" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_77734049-f52d-4e5c-b6e5-557f00db9af3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_7e95b338-7961-45a4-af17-678e9d15ef09" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_77734049-f52d-4e5c-b6e5-557f00db9af3" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_7e95b338-7961-45a4-af17-678e9d15ef09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityMember_41d5063d-7603-4433-bdc9-0159f168148b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_7e95b338-7961-45a4-af17-678e9d15ef09" xlink:to="loc_us-gaap_LiabilityMember_41d5063d-7603-4433-bdc9-0159f168148b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationPursuitDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationPursuitDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationPursuitDetails" xlink:type="extended" id="ic44f546530fa4711b46badacea18de84_FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationPursuitDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_ce9b3ca6-e0b6-4584-9784-0e78b003b2e0" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_ce9b3ca6-e0b6-4584-9784-0e78b003b2e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_3ebe37bd-1300-44c1-b71e-bbffeb10b064" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:to="loc_us-gaap_BusinessCombinationConsiderationTransferredLiabilitiesIncurred_3ebe37bd-1300-44c1-b71e-bbffeb10b064" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_eb82d2c9-2bd4-4a36-975e-8d37e331c03d" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_eb82d2c9-2bd4-4a36-975e-8d37e331c03d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CurrencyTranslationOnEarnOut_a87b72b9-1a10-46c0-9aab-1c9d630e4f54" xlink:href="icui-20220630.xsd#icui_CurrencyTranslationOnEarnOut"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:to="loc_icui_CurrencyTranslationOnEarnOut_a87b72b9-1a10-46c0-9aab-1c9d630e4f54" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_83c2baa4-f7b9-448b-aae1-11e2a3cbfa1b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_3ccf157a-293b-416f-aff0-6ddbb8ccc527" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_83c2baa4-f7b9-448b-aae1-11e2a3cbfa1b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_83c2baa4-f7b9-448b-aae1-11e2a3cbfa1b" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc_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_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_811ab4c2-3354-44e2-9d19-332b078cc69a" 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_2e0ff1c1-e292-4816-b84d-9b54d9fbf1cc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_811ab4c2-3354-44e2-9d19-332b078cc69a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_24ae3160-f154-4800-887b-e543f08acdb6" xlink:href="icui-20220630.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_811ab4c2-3354-44e2-9d19-332b078cc69a" xlink:to="loc_icui_PursuitVascularInc.Member_24ae3160-f154-4800-887b-e543f08acdb6" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationHospiraDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationHospiraDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationHospiraDetails" xlink:type="extended" id="ib2b3f3c009de4caf89a2d94153c219d1_FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationHospiraDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_65a8a356-ecbc-43ce-b6f6-f5c14c32115d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_1ed1c0c2-97f1-4a64-b19e-af1a91c04120" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_65a8a356-ecbc-43ce-b6f6-f5c14c32115d" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_1ed1c0c2-97f1-4a64-b19e-af1a91c04120" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_bf74a33f-87c8-408f-b372-987757c3ed05" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_65a8a356-ecbc-43ce-b6f6-f5c14c32115d" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_bf74a33f-87c8-408f-b372-987757c3ed05" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_65a8a356-ecbc-43ce-b6f6-f5c14c32115d" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_619d583e-c44c-4806-b837-c50440facd58" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_619d583e-c44c-4806-b837-c50440facd58" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_619d583e-c44c-4806-b837-c50440facd58_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_619d583e-c44c-4806-b837-c50440facd58" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_619d583e-c44c-4806-b837-c50440facd58_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_56bed086-3b90-40d2-a4f2-edd0ec3db41b" 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_619d583e-c44c-4806-b837-c50440facd58" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_56bed086-3b90-40d2-a4f2-edd0ec3db41b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_305fad12-c6fb-4dc1-8eef-688544869864" xlink:href="icui-20220630.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_56bed086-3b90-40d2-a4f2-edd0ec3db41b" xlink:to="loc_icui_PursuitVascularInc.Member_305fad12-c6fb-4dc1-8eef-688544869864" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_9345f063-ed22-471c-9648-97b78c3598e4" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_9345f063-ed22-471c-9648-97b78c3598e4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9345f063-ed22-471c-9648-97b78c3598e4_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_9345f063-ed22-471c-9648-97b78c3598e4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9345f063-ed22-471c-9648-97b78c3598e4_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_4761cbf0-d414-4e4f-8b5e-f9516a6eaa21" 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_9345f063-ed22-471c-9648-97b78c3598e4" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_4761cbf0-d414-4e4f-8b5e-f9516a6eaa21" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_33d64a90-2112-429d-9914-087ce1021205" 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_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_33d64a90-2112-429d-9914-087ce1021205" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_33d64a90-2112-429d-9914-087ce1021205_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_33d64a90-2112-429d-9914-087ce1021205" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_33d64a90-2112-429d-9914-087ce1021205_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_7b545858-b516-4da1-80d8-f17bab667bb2" 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_33d64a90-2112-429d-9914-087ce1021205" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_7b545858-b516-4da1-80d8-f17bab667bb2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_bb316df4-39dd-420f-918b-59a8c371716f" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_955f9991-3f2a-4a88-97a1-14c32f66a11c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_bb316df4-39dd-420f-918b-59a8c371716f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_bb316df4-39dd-420f-918b-59a8c371716f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_bb316df4-39dd-420f-918b-59a8c371716f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_bb316df4-39dd-420f-918b-59a8c371716f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_c086a43e-6601-441e-9721-5983bca46cb8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_bb316df4-39dd-420f-918b-59a8c371716f" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_c086a43e-6601-441e-9721-5983bca46cb8" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails" xlink:type="extended" id="if849c6f7264b45639af3eed129a64b6b_FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_9f527e33-3d92-4bc0-af11-d1a4fcac660a" 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_a199fc69-a73f-41e2-8caf-abb1d62e2aef" 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_9f527e33-3d92-4bc0-af11-d1a4fcac660a" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_a199fc69-a73f-41e2-8caf-abb1d62e2aef" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_551c84b8-59f7-4880-a516-db60419fc37c" 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_9f527e33-3d92-4bc0-af11-d1a4fcac660a" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_551c84b8-59f7-4880-a516-db60419fc37c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_bcda04b8-3e59-4345-8688-4fd1c12bc8dc" 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_551c84b8-59f7-4880-a516-db60419fc37c" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_bcda04b8-3e59-4345-8688-4fd1c12bc8dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bcda04b8-3e59-4345-8688-4fd1c12bc8dc_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_bcda04b8-3e59-4345-8688-4fd1c12bc8dc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_bcda04b8-3e59-4345-8688-4fd1c12bc8dc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35e35f5c-3064-4c04-9aee-f4758f5717c3" 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_bcda04b8-3e59-4345-8688-4fd1c12bc8dc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35e35f5c-3064-4c04-9aee-f4758f5717c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_PursuitVascularInc.Member_c3de3150-bcc7-4413-9abc-a2e2c2dadc4f" xlink:href="icui-20220630.xsd#icui_PursuitVascularInc.Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35e35f5c-3064-4c04-9aee-f4758f5717c3" xlink:to="loc_icui_PursuitVascularInc.Member_c3de3150-bcc7-4413-9abc-a2e2c2dadc4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_7c073c6e-fa7b-4a70-9a92-3de5db3a6e51" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_35e35f5c-3064-4c04-9aee-f4758f5717c3" xlink:to="loc_icui_SmithsMedicalMember_7c073c6e-fa7b-4a70-9a92-3de5db3a6e51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05" 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_551c84b8-59f7-4880-a516-db60419fc37c" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05_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_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_de7bd330-dfc7-4138-8bd1-15222c607cfe" 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_b8526eea-bc88-48bc-bdbf-0d33c0cdfa05" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MeasurementinputadjustedEBITDAvolatilityDomain_ff5cf105-eb58-4b18-b4a1-37fdce7994c8" xlink:href="icui-20220630.xsd#icui_MeasurementinputadjustedEBITDAvolatilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:to="loc_icui_MeasurementinputadjustedEBITDAvolatilityDomain_ff5cf105-eb58-4b18-b4a1-37fdce7994c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_d36669e9-1688-48a9-b775-8edda7aed74c" 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_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_d36669e9-1688-48a9-b775-8edda7aed74c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_bc812f0f-527d-42d0-b5f6-39903aa5f9d1" 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_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_bc812f0f-527d-42d0-b5f6-39903aa5f9d1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MeasurementInputMarketPriceofRiskDomain_3d1cb7ca-5b43-4e4f-b94d-42239c39ac49" xlink:href="icui-20220630.xsd#icui_MeasurementInputMarketPriceofRiskDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:to="loc_icui_MeasurementInputMarketPriceofRiskDomain_3d1cb7ca-5b43-4e4f-b94d-42239c39ac49" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MeasurementInputPriceVolatilityMember_e361e570-f17d-4ac2-8fc1-fa504075676b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputPriceVolatilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_de7bd330-dfc7-4138-8bd1-15222c607cfe" xlink:to="loc_us-gaap_MeasurementInputPriceVolatilityMember_e361e570-f17d-4ac2-8fc1-fa504075676b" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails" xlink:type="extended" id="i77737e4b043a49a5993fda3ab7034d34_FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_11c5c56e-4f86-42ae-a441-2a26dec356bc" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_11c5c56e-4f86-42ae-a441-2a26dec356bc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_83fc3ccb-f1aa-45d8-a1a4-8aa6977e70db" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_83fc3ccb-f1aa-45d8-a1a4-8aa6977e70db" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_3a1d908b-f320-43d1-a0e0-d4eedba06d30" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_3a1d908b-f320-43d1-a0e0-d4eedba06d30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_47780d7d-4d89-4842-a50a-ef98d8ae4c84" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_47780d7d-4d89-4842-a50a-ef98d8ae4c84" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_ff0f4bf6-ded9-46fa-bac9-f00a0116c758" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_InterestRateDerivativeLiabilitiesAtFairValue_ff0f4bf6-ded9-46fa-bac9-f00a0116c758" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_feb9be3d-ee92-416d-bca6-10f47bd1b16a" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_feb9be3d-ee92-416d-bca6-10f47bd1b16a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_3168ad4a-1459-4429-97df-74220e09afdf" 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_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_3168ad4a-1459-4429-97df-74220e09afdf" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_e1146bd4-5732-4229-8756-17c22b7b17ee" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_e1146bd4-5732-4229-8756-17c22b7b17ee" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_a99eb408-81cc-43c4-bb4f-c1ccec85448e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FinancialLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_a99eb408-81cc-43c4-bb4f-c1ccec85448e" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_84431ebb-5ca3-4722-9fb1-7a42c0ed4d10" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_a48bb895-1601-45c7-88a7-bc6c7e64edf1" 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_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_a48bb895-1601-45c7-88a7-bc6c7e64edf1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a48bb895-1601-45c7-88a7-bc6c7e64edf1_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_a48bb895-1601-45c7-88a7-bc6c7e64edf1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a48bb895-1601-45c7-88a7-bc6c7e64edf1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b0125f42-90f6-4e40-b77b-9067b0ab689a" 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_a48bb895-1601-45c7-88a7-bc6c7e64edf1" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b0125f42-90f6-4e40-b77b-9067b0ab689a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_ac1ced5d-afe0-44de-abfb-e97eec555393" 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_b0125f42-90f6-4e40-b77b-9067b0ab689a" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_ac1ced5d-afe0-44de-abfb-e97eec555393" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_1e0daf64-9b3c-466d-a373-3f06cb0a0c79" 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_b0125f42-90f6-4e40-b77b-9067b0ab689a" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_1e0daf64-9b3c-466d-a373-3f06cb0a0c79" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_39614a19-8810-45f4-b46d-55dad6559a01" 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_b0125f42-90f6-4e40-b77b-9067b0ab689a" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_39614a19-8810-45f4-b46d-55dad6559a01" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_93a2fa6c-481e-4999-8cf7-999a625ccd14" 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_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_93a2fa6c-481e-4999-8cf7-999a625ccd14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_93a2fa6c-481e-4999-8cf7-999a625ccd14_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_93a2fa6c-481e-4999-8cf7-999a625ccd14" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_93a2fa6c-481e-4999-8cf7-999a625ccd14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_987b1bf2-738d-447d-aae5-52a3bab55819" 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_93a2fa6c-481e-4999-8cf7-999a625ccd14" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_d1460688-c830-4652-b749-9d8e551c2cdc" 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_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_d1460688-c830-4652-b749-9d8e551c2cdc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_76c87889-c3f0-4a88-a356-f7bf04f88282" 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_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_76c87889-c3f0-4a88-a356-f7bf04f88282" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_fc932ef1-2346-428a-bed1-2d77c2c96012" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_fc932ef1-2346-428a-bed1-2d77c2c96012" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsMember_435ee4ba-e559-4b08-a552-670ff4738c17" 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_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:to="loc_us-gaap_OtherAssetsMember_435ee4ba-e559-4b08-a552-670ff4738c17" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesMember_5d4e5a08-fc44-40ec-b3cc-eb515a8f48c7" 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_987b1bf2-738d-447d-aae5-52a3bab55819" xlink:to="loc_us-gaap_OtherLiabilitiesMember_5d4e5a08-fc44-40ec-b3cc-eb515a8f48c7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_e2cb9a1e-083b-444b-a2ef-1f3083680248" 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_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_e2cb9a1e-083b-444b-a2ef-1f3083680248" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e2cb9a1e-083b-444b-a2ef-1f3083680248_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_e2cb9a1e-083b-444b-a2ef-1f3083680248" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_e2cb9a1e-083b-444b-a2ef-1f3083680248_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" 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_e2cb9a1e-083b-444b-a2ef-1f3083680248" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EarnoutliabilityMember_db0fd098-cc0e-4444-aa27-40a26968d5d4" xlink:href="icui-20220630.xsd#icui_EarnoutliabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" xlink:to="loc_icui_EarnoutliabilityMember_db0fd098-cc0e-4444-aa27-40a26968d5d4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesTotalMember_7c87ce10-8782-4ef0-835a-ede8a79980cc" 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_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" xlink:to="loc_us-gaap_LiabilitiesTotalMember_7c87ce10-8782-4ef0-835a-ede8a79980cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EarnOutLiabilityST_f3db2264-17c6-482f-8627-ad7abc1085c8" xlink:href="icui-20220630.xsd#icui_EarnOutLiabilityST"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" xlink:to="loc_icui_EarnOutLiabilityST_f3db2264-17c6-482f-8627-ad7abc1085c8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_STEarnoutLiabilityMember_b19c17bd-52ef-451d-bd19-3bbf438c6ac0" xlink:href="icui-20220630.xsd#icui_STEarnoutLiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_8650ac03-06b8-4dfc-99a0-d4b648c2a73e" xlink:to="loc_icui_STEarnoutLiabilityMember_b19c17bd-52ef-451d-bd19-3bbf438c6ac0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_c01e6a97-17f6-4a3c-ad08-5291aafe78a7" 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_FairValueByBalanceSheetGroupingTable_c25ad4bc-35c3-410b-8dc9-6ec52915a70b" xlink:to="loc_us-gaap_InvestmentTypeAxis_c01e6a97-17f6-4a3c-ad08-5291aafe78a7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_c01e6a97-17f6-4a3c-ad08-5291aafe78a7_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_c01e6a97-17f6-4a3c-ad08-5291aafe78a7" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_c01e6a97-17f6-4a3c-ad08-5291aafe78a7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_10e668e5-9d7d-44df-b3be-627004f0b331" 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_c01e6a97-17f6-4a3c-ad08-5291aafe78a7" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_10e668e5-9d7d-44df-b3be-627004f0b331" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_68ee3c38-9c3f-4eb5-830a-9538386c32b9" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_10e668e5-9d7d-44df-b3be-627004f0b331" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_68ee3c38-9c3f-4eb5-830a-9538386c32b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_39eb5b45-7dd0-4fdd-b23d-6a4137a89809" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_10e668e5-9d7d-44df-b3be-627004f0b331" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_39eb5b45-7dd0-4fdd-b23d-6a4137a89809" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/InvestmentSecuritiesTableDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#InvestmentSecuritiesTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/InvestmentSecuritiesTableDetails" xlink:type="extended" id="i9e88c50964d14d3ba738603ac15af9f1_InvestmentSecuritiesTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" 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_AvailableForSaleSecuritiesDebtSecuritiesCurrent_3b793d8d-972d-4b42-8627-29fc195faa7e" 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_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_3b793d8d-972d-4b42-8627-29fc195faa7e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent_2e40ff2c-18fd-4207-84ec-b17da5eb8b39" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostNoncurrent_2e40ff2c-18fd-4207-84ec-b17da5eb8b39" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_6839ada3-2da9-4b11-aab4-5e54af163805" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPosition12MonthsOrLonger_6839ada3-2da9-4b11-aab4-5e54af163805" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_35a1345e-bfd4-4df7-af50-caa9cfd9d143" 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_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis_35a1345e-bfd4-4df7-af50-caa9cfd9d143" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_652073ad-a24e-4563-88d6-c2a2746f4866" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleAmortizedCostCurrent_652073ad-a24e-4563-88d6-c2a2746f4866" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_14caf6ea-9698-4fea-b313-a4bb888a21d8" 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_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesNoncurrent_14caf6ea-9698-4fea-b313-a4bb888a21d8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_128daf0f-0bf6-4bc9-8d8d-74d366c44314" 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_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecurities_128daf0f-0bf6-4bc9-8d8d-74d366c44314" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedLoss_7fea62c1-f628-47b5-9ea5-281844cbd4e2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_AvailableForSaleDebtSecuritiesGrossUnrealizedLoss_7fea62c1-f628-47b5-9ea5-281844cbd4e2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_89773a6e-f8c2-4580-9dcd-ce351cf7c22a" 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_38ebc446-2398-4b6d-a447-1007a7382cac" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_89773a6e-f8c2-4580-9dcd-ce351cf7c22a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_22830ea2-698c-458e-874a-597aa752e435" 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_89773a6e-f8c2-4580-9dcd-ce351cf7c22a" xlink:to="loc_us-gaap_InvestmentTypeAxis_22830ea2-698c-458e-874a-597aa752e435" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_22830ea2-698c-458e-874a-597aa752e435_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_22830ea2-698c-458e-874a-597aa752e435" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_22830ea2-698c-458e-874a-597aa752e435_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" 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_22830ea2-698c-458e-874a-597aa752e435" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_AvailableforsaleDebtSecurityCurrentMember_1c50d12e-5794-4bc6-af19-ff22602b2813" xlink:href="icui-20220630.xsd#icui_AvailableforsaleDebtSecurityCurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" xlink:to="loc_icui_AvailableforsaleDebtSecurityCurrentMember_1c50d12e-5794-4bc6-af19-ff22602b2813" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongtermInvestmentsDomain_94668a46-58eb-4ab5-a0a8-cafda21c73a8" xlink:href="icui-20220630.xsd#icui_LongtermInvestmentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" xlink:to="loc_icui_LongtermInvestmentsDomain_94668a46-58eb-4ab5-a0a8-cafda21c73a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateBondSecuritiesMember_b552b426-da0d-47fd-ab89-76673ee1f657" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CorporateBondSecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" xlink:to="loc_us-gaap_CorporateBondSecuritiesMember_b552b426-da0d-47fd-ab89-76673ee1f657" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_USTreasurySecuritiesMember_5911cfe5-fdbb-4458-83b8-b22007f40ddd" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_USTreasurySecuritiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_3be230b6-b72c-4bdb-973f-38fa429149f6" xlink:to="loc_us-gaap_USTreasurySecuritiesMember_5911cfe5-fdbb-4458-83b8-b22007f40ddd" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/OtherAssetsNoncurrentDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#OtherAssetsNoncurrentDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/OtherAssetsNoncurrentDetails" xlink:type="extended" id="i567df78dd57545408576fc63684701e6_OtherAssetsNoncurrentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_d3b809dc-b6df-42a7-b35b-5869c6d1df31" 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_DerivativeAssetsNoncurrent_45c0d15f-04f8-4486-bf91-1bf0799d0780" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d3b809dc-b6df-42a7-b35b-5869c6d1df31" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_45c0d15f-04f8-4486-bf91-1bf0799d0780" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_f04d67cf-5944-4f01-840e-9d54f965bcbf" 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_d3b809dc-b6df-42a7-b35b-5869c6d1df31" xlink:to="loc_us-gaap_DerivativeTable_f04d67cf-5944-4f01-840e-9d54f965bcbf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_542b6183-0a83-4571-aab2-e0bc0cea6f50" 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_f04d67cf-5944-4f01-840e-9d54f965bcbf" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_542b6183-0a83-4571-aab2-e0bc0cea6f50" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_542b6183-0a83-4571-aab2-e0bc0cea6f50_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_542b6183-0a83-4571-aab2-e0bc0cea6f50" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_542b6183-0a83-4571-aab2-e0bc0cea6f50_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ca6b0e85-1bd8-4ef1-8c79-2dafbf549aad" 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_542b6183-0a83-4571-aab2-e0bc0cea6f50" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ca6b0e85-1bd8-4ef1-8c79-2dafbf549aad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_3e49188c-3ee7-4a4a-93f8-78e4c27ad870" 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_ca6b0e85-1bd8-4ef1-8c79-2dafbf549aad" xlink:to="loc_us-gaap_InterestRateSwapMember_3e49188c-3ee7-4a4a-93f8-78e4c27ad870" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeMember_c868cac0-4bd8-46bf-aa48-d4accbc5e153" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_ca6b0e85-1bd8-4ef1-8c79-2dafbf549aad" xlink:to="loc_us-gaap_ForeignExchangeMember_c868cac0-4bd8-46bf-aa48-d4accbc5e153" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/PropertyandEquipmentDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#PropertyandEquipmentDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PropertyandEquipmentDetails" xlink:type="extended" id="i84b3c310c68a4e9ea063343bd99192a1_PropertyandEquipmentDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f5fa7841-1227-49b3-b1b6-5c8752f21f46" 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_427aa31f-c9cf-4010-9d51-e07cecdec5ed" 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_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_427aa31f-c9cf-4010-9d51-e07cecdec5ed" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_5e687461-b5b6-4c3f-b46a-0ba2a9467633" 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_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_5e687461-b5b6-4c3f-b46a-0ba2a9467633" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_a0d2474c-d027-4c0d-b23b-2ba9b2e142ac" 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_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_a0d2474c-d027-4c0d-b23b-2ba9b2e142ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MachineryAndEquipmentGross_b2a2d5a4-c4a0-4485-8b5a-4ec93e2202d0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MachineryAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_MachineryAndEquipmentGross_b2a2d5a4-c4a0-4485-8b5a-4ec93e2202d0" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FurnitureAndFixturesGross_59018c90-aa11-4203-96ae-7d2c44072617" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_FurnitureAndFixturesGross_59018c90-aa11-4203-96ae-7d2c44072617" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConstructionInProgressGross_dd62c57d-f64b-49c6-9541-8ced2f6f700e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConstructionInProgressGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_ConstructionInProgressGross_dd62c57d-f64b-49c6-9541-8ced2f6f700e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3eb37b61-9161-4dcc-93be-fa16091ddddc" 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_f5fa7841-1227-49b3-b1b6-5c8752f21f46" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_3eb37b61-9161-4dcc-93be-fa16091ddddc" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1887b503-9a82-4017-a1f1-8bccabf2170d" 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_3eb37b61-9161-4dcc-93be-fa16091ddddc" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_1887b503-9a82-4017-a1f1-8bccabf2170d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1887b503-9a82-4017-a1f1-8bccabf2170d_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_1887b503-9a82-4017-a1f1-8bccabf2170d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_1887b503-9a82-4017-a1f1-8bccabf2170d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_174e3166-23f8-4033-838b-716e8746e0e6" 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_1887b503-9a82-4017-a1f1-8bccabf2170d" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_174e3166-23f8-4033-838b-716e8746e0e6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_e1b80315-c02d-46f3-a81b-62dad08a72e4" 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_174e3166-23f8-4033-838b-716e8746e0e6" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_e1b80315-c02d-46f3-a81b-62dad08a72e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_MoldsMember_3de78c2d-1651-4171-a8ed-563154f3c33d" xlink:href="icui-20220630.xsd#icui_MoldsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_174e3166-23f8-4033-838b-716e8746e0e6" xlink:to="loc_icui_MoldsMember_3de78c2d-1651-4171-a8ed-563154f3c33d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ComputerEquipmentAndSoftwareMember_4583ee06-03e8-4945-8e3b-14c7626e02b1" xlink:href="icui-20220630.xsd#icui_ComputerEquipmentAndSoftwareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_174e3166-23f8-4033-838b-716e8746e0e6" xlink:to="loc_icui_ComputerEquipmentAndSoftwareMember_4583ee06-03e8-4945-8e3b-14c7626e02b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InstrumentsPlacedwithCustomersMember_6406db55-56d2-494b-bbed-db9ff3acc6be" xlink:href="icui-20220630.xsd#icui_InstrumentsPlacedwithCustomersMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_174e3166-23f8-4033-838b-716e8746e0e6" xlink:to="loc_icui_InstrumentsPlacedwithCustomersMember_6406db55-56d2-494b-bbed-db9ff3acc6be" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillandIntangibleAssetsIntangiblesTableDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#GoodwillandIntangibleAssetsIntangiblesTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillandIntangibleAssetsIntangiblesTableDetails" xlink:type="extended" id="ia96db5644a454880a8ff427f98b68893_GoodwillandIntangibleAssetsIntangiblesTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e666c3ed-9459-4367-b32c-42be717f2e89" 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_570013a9-8ead-4f6a-9a78-901ef661543b" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_570013a9-8ead-4f6a-9a78-901ef661543b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_15ff01a2-8716-47b7-b61e-9eee9acf14e5" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_15ff01a2-8716-47b7-b61e-9eee9acf14e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ea074800-2c4a-4567-81c4-22b15c2146aa" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_ea074800-2c4a-4567-81c4-22b15c2146aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7038a2ab-4de7-4d65-acb0-61eca9693679" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7038a2ab-4de7-4d65-acb0-61eca9693679" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_9eec40c4-84ff-4d5f-b7d1-f3168e9887af" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_9eec40c4-84ff-4d5f-b7d1-f3168e9887af" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_da741338-e516-402c-9839-da6f5ace68df" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_da741338-e516-402c-9839-da6f5ace68df" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_437dde1e-3967-4209-8180-6a3a5acfc74c" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_437dde1e-3967-4209-8180-6a3a5acfc74c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" 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_e666c3ed-9459-4367-b32c-42be717f2e89" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_542bd84a-cc3b-4f2f-9bc3-cee43779add3" 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_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_542bd84a-cc3b-4f2f-9bc3-cee43779add3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_542bd84a-cc3b-4f2f-9bc3-cee43779add3_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_542bd84a-cc3b-4f2f-9bc3-cee43779add3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_542bd84a-cc3b-4f2f-9bc3-cee43779add3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_443a9289-8d85-4732-ac32-9a5a7d60c4fc" 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_542bd84a-cc3b-4f2f-9bc3-cee43779add3" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_17df1e57-0ebe-4523-85e0-06eaa1704356" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_PatentsMember_17df1e57-0ebe-4523-85e0-06eaa1704356" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_1791e962-1b52-4fb1-a344-cf6a67a6b76e" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_CustomerContractsMember_1791e962-1b52-4fb1-a344-cf6a67a6b76e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_2b695667-88bb-4f66-8bdd-7f47afd23fe9" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_2b695667-88bb-4f66-8bdd-7f47afd23fe9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_afba8cc3-98f8-4f9c-858d-9f5f00984c86" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_TrademarksMember_afba8cc3-98f8-4f9c-858d-9f5f00984c86" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_35a55a2f-8797-4f07-9327-272914131676" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_TradeNamesMember_35a55a2f-8797-4f07-9327-272914131676" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_f7ba6899-0f66-4fff-b2a9-30fdb7044a22" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_f7ba6899-0f66-4fff-b2a9-30fdb7044a22" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_e87d9900-d9e8-4e73-a07b-ba1d2c9ed920" 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_443a9289-8d85-4732-ac32-9a5a7d60c4fc" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_e87d9900-d9e8-4e73-a07b-ba1d2c9ed920" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_63a0b1c0-075a-4f01-be3c-eed20db54492" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" xlink:to="loc_srt_ConsolidationItemsAxis_63a0b1c0-075a-4f01-be3c-eed20db54492" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_63a0b1c0-075a-4f01-be3c-eed20db54492_default" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_63a0b1c0-075a-4f01-be3c-eed20db54492" xlink:to="loc_srt_ConsolidationItemsDomain_63a0b1c0-075a-4f01-be3c-eed20db54492_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_a5e51864-fa22-4456-a1f7-e4605d1fa0aa" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_63a0b1c0-075a-4f01-be3c-eed20db54492" xlink:to="loc_srt_ConsolidationItemsDomain_a5e51864-fa22-4456-a1f7-e4605d1fa0aa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_4f02525e-95d1-45b3-a4af-25cf5f9813f8" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_4f02525e-95d1-45b3-a4af-25cf5f9813f8" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_4f02525e-95d1-45b3-a4af-25cf5f9813f8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4f02525e-95d1-45b3-a4af-25cf5f9813f8" xlink:to="loc_us-gaap_SegmentDomain_4f02525e-95d1-45b3-a4af-25cf5f9813f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_0fde0e82-e6a5-4dab-a787-a1eb52c1e5d6" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_4f02525e-95d1-45b3-a4af-25cf5f9813f8" xlink:to="loc_us-gaap_SegmentDomain_0fde0e82-e6a5-4dab-a787-a1eb52c1e5d6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_ab11aebd-9e5f-434e-98bd-35c41f017103" 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_ScheduleOfFiniteLivedIntangibleAssetsTable_7b8a4b3a-e6ab-4fda-a37e-90006829ab7a" xlink:to="loc_srt_RangeAxis_ab11aebd-9e5f-434e-98bd-35c41f017103" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_ab11aebd-9e5f-434e-98bd-35c41f017103_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_ab11aebd-9e5f-434e-98bd-35c41f017103" xlink:to="loc_srt_RangeMember_ab11aebd-9e5f-434e-98bd-35c41f017103_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_7f2f7490-3b8a-4ddd-860e-b69b452ea97e" 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_ab11aebd-9e5f-434e-98bd-35c41f017103" xlink:to="loc_srt_RangeMember_7f2f7490-3b8a-4ddd-860e-b69b452ea97e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#AccruedLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:type="extended" id="i0d80ff532c2d43eda69d429b1bd93170_AccruedLiabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_6adc765c-e8bd-4ede-9c52-66b666aa8ef7" 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_DerivativeLiabilitiesCurrent_2a01d604-66dd-480f-a681-e3e1fc2eab88" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_6adc765c-e8bd-4ede-9c52-66b666aa8ef7" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_2a01d604-66dd-480f-a681-e3e1fc2eab88" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_dfd1f491-2f67-4460-a22d-cd067d768428" 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_6adc765c-e8bd-4ede-9c52-66b666aa8ef7" xlink:to="loc_us-gaap_DerivativeTable_dfd1f491-2f67-4460-a22d-cd067d768428" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_b58f128a-6083-482a-b640-77f9b9fbff4e" 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_dfd1f491-2f67-4460-a22d-cd067d768428" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_b58f128a-6083-482a-b640-77f9b9fbff4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_b58f128a-6083-482a-b640-77f9b9fbff4e_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_b58f128a-6083-482a-b640-77f9b9fbff4e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_b58f128a-6083-482a-b640-77f9b9fbff4e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_09b479e3-a0d1-4d44-b6c0-b2dc7ec4058d" 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_b58f128a-6083-482a-b640-77f9b9fbff4e" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_09b479e3-a0d1-4d44-b6c0-b2dc7ec4058d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeMember_6d7992bc-fbf5-47ff-aa2d-5055eea0e193" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_09b479e3-a0d1-4d44-b6c0-b2dc7ec4058d" xlink:to="loc_us-gaap_ForeignExchangeMember_6d7992bc-fbf5-47ff-aa2d-5055eea0e193" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyLineItems_72b87451-f04d-42e4-b31b-c5ef1ff6f6d3" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_1a1b0a5b-d6f6-4d90-9ce2-c548aa928022" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_72b87451-f04d-42e4-b31b-c5ef1ff6f6d3" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_1a1b0a5b-d6f6-4d90-9ce2-c548aa928022" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyTable_f8a39fc1-ba46-4709-8d27-fd4129221803" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_72b87451-f04d-42e4-b31b-c5ef1ff6f6d3" xlink:to="loc_us-gaap_ProductLiabilityContingencyTable_f8a39fc1-ba46-4709-8d27-fd4129221803" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16" xlink:href="icui-20220630.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ProductLiabilityContingencyTable_f8a39fc1-ba46-4709-8d27-fd4129221803" xlink:to="loc_icui_TimingAxis_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16_default" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16" xlink:to="loc_icui_TimingDomain_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_5ba33fb1-07d4-461f-b3b8-2023ef2c09dc" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_0b09f8c4-c89b-4a9f-91b0-7e87a3fbbd16" xlink:to="loc_icui_TimingDomain_5ba33fb1-07d4-461f-b3b8-2023ef2c09dc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermMember_0da79ce5-010f-48cb-867d-1503d0e59037" xlink:href="icui-20220630.xsd#icui_ShortTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_5ba33fb1-07d4-461f-b3b8-2023ef2c09dc" xlink:to="loc_icui_ShortTermMember_0da79ce5-010f-48cb-867d-1503d0e59037" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesLongtermliabilitiesDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#AccruedLiabilitiesLongtermliabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesLongtermliabilitiesDetails" xlink:type="extended" id="ibeaa40eeef114644b0dfffffdf8899a4_AccruedLiabilitiesLongtermliabilitiesDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyLineItems_63368949-4749-4287-841a-8814ae750144" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_43008444-cc60-4af1-91f5-69b232cad90d" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_63368949-4749-4287-841a-8814ae750144" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_43008444-cc60-4af1-91f5-69b232cad90d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_64544f59-a59b-4afe-951f-ea7d676a4495" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_63368949-4749-4287-841a-8814ae750144" xlink:to="loc_us-gaap_ContractWithCustomerLiabilityNoncurrent_64544f59-a59b-4afe-951f-ea7d676a4495" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyTable_81861f7b-b91f-4eba-9f3b-8004239ad2d2" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_63368949-4749-4287-841a-8814ae750144" xlink:to="loc_us-gaap_ProductLiabilityContingencyTable_81861f7b-b91f-4eba-9f3b-8004239ad2d2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_c65e4f26-a575-4887-88a6-fc7d42e1a884" xlink:href="icui-20220630.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ProductLiabilityContingencyTable_81861f7b-b91f-4eba-9f3b-8004239ad2d2" xlink:to="loc_icui_TimingAxis_c65e4f26-a575-4887-88a6-fc7d42e1a884" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_c65e4f26-a575-4887-88a6-fc7d42e1a884_default" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_c65e4f26-a575-4887-88a6-fc7d42e1a884" xlink:to="loc_icui_TimingDomain_c65e4f26-a575-4887-88a6-fc7d42e1a884_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_4bba79a3-1d96-4e4e-85ae-e7e9b5aa6f10" xlink:href="icui-20220630.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_c65e4f26-a575-4887-88a6-fc7d42e1a884" xlink:to="loc_icui_TimingDomain_4bba79a3-1d96-4e4e-85ae-e7e9b5aa6f10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermMember_c14e0774-adf7-4df0-8141-4666b04130db" xlink:href="icui-20220630.xsd#icui_LongTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_4bba79a3-1d96-4e4e-85ae-e7e9b5aa6f10" xlink:to="loc_icui_LongTermMember_c14e0774-adf7-4df0-8141-4666b04130db" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_396a9b35-5f53-486e-a940-bab872335ae6" 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_DerivativeLiabilitiesNoncurrent_92394bcf-555a-4a89-9ed4-94f0058a3202" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DerivativeLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_396a9b35-5f53-486e-a940-bab872335ae6" xlink:to="loc_us-gaap_DerivativeLiabilitiesNoncurrent_92394bcf-555a-4a89-9ed4-94f0058a3202" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_61d2451e-4d84-4f11-9c86-ec3a9b55563a" 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_396a9b35-5f53-486e-a940-bab872335ae6" xlink:to="loc_us-gaap_DerivativeTable_61d2451e-4d84-4f11-9c86-ec3a9b55563a" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5707178a-0365-4db6-942b-dd32b87ca58c" 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_61d2451e-4d84-4f11-9c86-ec3a9b55563a" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5707178a-0365-4db6-942b-dd32b87ca58c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5707178a-0365-4db6-942b-dd32b87ca58c_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_5707178a-0365-4db6-942b-dd32b87ca58c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5707178a-0365-4db6-942b-dd32b87ca58c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ae932aba-8770-4eaa-bee9-07ccb7fa2a3d" 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_5707178a-0365-4db6-942b-dd32b87ca58c" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ae932aba-8770-4eaa-bee9-07ccb7fa2a3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeMember_a4529882-a86f-4985-917a-592ac49344dc" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_ae932aba-8770-4eaa-bee9-07ccb7fa2a3d" xlink:to="loc_us-gaap_ForeignExchangeMember_a4529882-a86f-4985-917a-592ac49344dc" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#LongTermObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="extended" id="i891f713578984d58849fcb89a732d739_LongTermObligationsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" 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_icui_TotalSeniorSecuredCreditFacility_bc483222-d0bd-4985-b21c-5ba2bf944d2b" xlink:href="icui-20220630.xsd#icui_TotalSeniorSecuredCreditFacility"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_icui_TotalSeniorSecuredCreditFacility_bc483222-d0bd-4985-b21c-5ba2bf944d2b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfDebt_7288e4b5-ea43-4fa7-99c7-0aeb330050e5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromIssuanceOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfDebt_7288e4b5-ea43-4fa7-99c7-0aeb330050e5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_28e44ffc-8f4d-4ee2-ba94-697d1f157052" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_28e44ffc-8f4d-4ee2-ba94-697d1f157052" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RevolverSubLimits_b721067f-6b79-4804-b13c-2edf9d4a45fb" xlink:href="icui-20220630.xsd#icui_RevolverSubLimits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_icui_RevolverSubLimits_b721067f-6b79-4804-b13c-2edf9d4a45fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_66a06f56-1a95-4218-8079-2c9ec71e3780" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_66a06f56-1a95-4218-8079-2c9ec71e3780" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_e80269e9-a6db-418c-a88c-e255d2bbbf3c" 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_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_LongTermDebt_e80269e9-a6db-418c-a88c-e255d2bbbf3c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_19634170-da21-466e-8b7d-1cd016e4d79c" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_19634170-da21-466e-8b7d-1cd016e4d79c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioCalculationCeilingSubtractedAmount_efbd7af8-727c-40e6-aa9a-1fc00da6dcf7" xlink:href="icui-20220630.xsd#icui_LeverageRatioCalculationCeilingSubtractedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_icui_LeverageRatioCalculationCeilingSubtractedAmount_efbd7af8-727c-40e6-aa9a-1fc00da6dcf7" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_ec7acefc-a391-49fc-8e11-3d7b78276326" 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_9b243b28-6c09-4496-ad6d-cbfc17ad78ab" xlink:to="loc_us-gaap_DebtInstrumentTable_ec7acefc-a391-49fc-8e11-3d7b78276326" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ec7acefc-a391-49fc-8e11-3d7b78276326" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_3b933f46-a2e7-4803-99f2-9d67345dedc5" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_5d9b7129-6f6b-45e2-b1f9-35320f0aa36e" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_3b933f46-a2e7-4803-99f2-9d67345dedc5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_e2593a4d-1c00-4dce-af95-5391dd4b9d98" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_3b933f46-a2e7-4803-99f2-9d67345dedc5" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_e2593a4d-1c00-4dce-af95-5391dd4b9d98" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_ef043979-7abc-4cb4-abc5-28daaf77ea55" xlink:href="icui-20220630.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_ec7acefc-a391-49fc-8e11-3d7b78276326" xlink:to="loc_icui_TermLoanAxis_ef043979-7abc-4cb4-abc5-28daaf77ea55" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_ef043979-7abc-4cb4-abc5-28daaf77ea55_default" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_ef043979-7abc-4cb4-abc5-28daaf77ea55" xlink:to="loc_icui_TermLoanDomain_ef043979-7abc-4cb4-abc5-28daaf77ea55_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_fa133a2e-2694-4ad3-84f4-57dbdc706132" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_ef043979-7abc-4cb4-abc5-28daaf77ea55" xlink:to="loc_icui_TermLoanDomain_fa133a2e-2694-4ad3-84f4-57dbdc706132" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_a378b002-8dc3-4f42-9178-62d8bc8712b8" xlink:href="icui-20220630.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_fa133a2e-2694-4ad3-84f4-57dbdc706132" xlink:to="loc_icui_TermLoanAMember_a378b002-8dc3-4f42-9178-62d8bc8712b8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_4ff2b76d-0aaa-4abe-8121-83ceb6e027a1" xlink:href="icui-20220630.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_fa133a2e-2694-4ad3-84f4-57dbdc706132" xlink:to="loc_icui_TermLoanBMember_4ff2b76d-0aaa-4abe-8121-83ceb6e027a1" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsInterestRateTermsDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#LongTermObligationsInterestRateTermsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsInterestRateTermsDetails" xlink:type="extended" id="idd73d09222a74414a3a55dfaacfa4205_LongTermObligationsInterestRateTermsDetails">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:href="icui-20220630.xsd#icui_ApplicableMarginBasedOnLeverageRatioLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBaseRateLoans_21d69751-3fee-4021-916d-7055e654e817" xlink:href="icui-20220630.xsd#icui_ApplicableMarginBaseRateLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:to="loc_icui_ApplicableMarginBaseRateLoans_21d69751-3fee-4021-916d-7055e654e817" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginTermSOFRLoans_a532f38b-098a-4739-9d21-6f40104bef5d" xlink:href="icui-20220630.xsd#icui_ApplicableMarginTermSOFRLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:to="loc_icui_ApplicableMarginTermSOFRLoans_a532f38b-098a-4739-9d21-6f40104bef5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f014bbbf-6cad-44d4-858a-16881b3d3cd6" 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_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_f014bbbf-6cad-44d4-858a-16881b3d3cd6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans_4dd40f14-4cab-4511-829c-3b7ad9b7609a" xlink:href="icui-20220630.xsd#icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:to="loc_icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans_4dd40f14-4cab-4511-829c-3b7ad9b7609a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_3a511c99-afbc-492e-84b3-e0dacfcfff72" xlink:href="icui-20220630.xsd#icui_ApplicableMarginBasedOnLeverageRatioTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_089b5a89-3e90-4a14-b95f-b656ed8621a2" xlink:to="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_3a511c99-afbc-492e-84b3-e0dacfcfff72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_c7b317b7-c198-4a5f-8f64-3f5cf37c076e" xlink:href="icui-20220630.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_3a511c99-afbc-492e-84b3-e0dacfcfff72" xlink:to="loc_icui_TermLoanAxis_c7b317b7-c198-4a5f-8f64-3f5cf37c076e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_c7b317b7-c198-4a5f-8f64-3f5cf37c076e_default" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_c7b317b7-c198-4a5f-8f64-3f5cf37c076e" xlink:to="loc_icui_TermLoanDomain_c7b317b7-c198-4a5f-8f64-3f5cf37c076e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_06ff857c-6fcd-4324-82e4-baa9d4377762" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_c7b317b7-c198-4a5f-8f64-3f5cf37c076e" xlink:to="loc_icui_TermLoanDomain_06ff857c-6fcd-4324-82e4-baa9d4377762" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_c35f511d-93a8-4d8e-a27c-14fb80801eb0" xlink:href="icui-20220630.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_06ff857c-6fcd-4324-82e4-baa9d4377762" xlink:to="loc_icui_TermLoanAMember_c35f511d-93a8-4d8e-a27c-14fb80801eb0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_554a1a15-7c81-4495-ba64-0addc3f41ca4" xlink:href="icui-20220630.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_06ff857c-6fcd-4324-82e4-baa9d4377762" xlink:to="loc_icui_TermLoanBMember_554a1a15-7c81-4495-ba64-0addc3f41ca4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelAxis_b3468c16-11be-4efa-96a9-83c1f43e9ced" xlink:href="icui-20220630.xsd#icui_LeverageRatioLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_3a511c99-afbc-492e-84b3-e0dacfcfff72" xlink:to="loc_icui_LeverageRatioLevelAxis_b3468c16-11be-4efa-96a9-83c1f43e9ced" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelDomain_b3468c16-11be-4efa-96a9-83c1f43e9ced_default" xlink:href="icui-20220630.xsd#icui_LeverageRatioLevelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_LeverageRatioLevelAxis_b3468c16-11be-4efa-96a9-83c1f43e9ced" xlink:to="loc_icui_LeverageRatioLevelDomain_b3468c16-11be-4efa-96a9-83c1f43e9ced_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:href="icui-20220630.xsd#icui_LeverageRatioLevelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_LeverageRatioLevelAxis_b3468c16-11be-4efa-96a9-83c1f43e9ced" xlink:to="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Greaterthan400to100Member_6b878b94-b934-41ae-a118-1f82dae9bf3e" xlink:href="icui-20220630.xsd#icui_Greaterthan400to100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_Greaterthan400to100Member_6b878b94-b934-41ae-a118-1f82dae9bf3e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member_abebcae5-6712-4838-abca-b80f8fed8e32" xlink:href="icui-20220630.xsd#icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member_abebcae5-6712-4838-abca-b80f8fed8e32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqual300To100ButGreaterThan250to100Member_8d612a7f-2936-4afa-b6c0-ef526460c75b" xlink:href="icui-20220630.xsd#icui_LessThanOrEqual300To100ButGreaterThan250to100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_LessThanOrEqual300To100ButGreaterThan250to100Member_8d612a7f-2936-4afa-b6c0-ef526460c75b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member_cf7bcab2-fc39-49db-8b69-4e8d08adefae" xlink:href="icui-20220630.xsd#icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member_cf7bcab2-fc39-49db-8b69-4e8d08adefae" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo200To100Member_30ee325c-3f92-4bcc-91af-35a9d0034f1e" xlink:href="icui-20220630.xsd#icui_LessThanOrEqualTo200To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_LessThanOrEqualTo200To100Member_30ee325c-3f92-4bcc-91af-35a9d0034f1e" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GreaterThan275To100Member_87810cd0-adca-4292-b71b-d63e67caad44" xlink:href="icui-20220630.xsd#icui_GreaterThan275To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_GreaterThan275To100Member_87810cd0-adca-4292-b71b-d63e67caad44" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThan275To100Member_1e3031b5-dd5b-4ebb-9414-eb8d900959b4" xlink:href="icui-20220630.xsd#icui_LessThan275To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_065ea96a-e8d1-4ac8-9404-321f805e1d48" xlink:to="loc_icui_LessThan275To100Member_1e3031b5-dd5b-4ebb-9414-eb8d900959b4" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_a312379d-f308-40e3-a9c2-4b7b027edc28" 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_icui_ApplicableMarginBasedOnLeverageRatioTable_3a511c99-afbc-492e-84b3-e0dacfcfff72" xlink:to="loc_srt_RangeAxis_a312379d-f308-40e3-a9c2-4b7b027edc28" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_a312379d-f308-40e3-a9c2-4b7b027edc28_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_a312379d-f308-40e3-a9c2-4b7b027edc28" xlink:to="loc_srt_RangeMember_a312379d-f308-40e3-a9c2-4b7b027edc28_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_2459fd56-8312-4a53-9835-fa8a011a3e68" 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_a312379d-f308-40e3-a9c2-4b7b027edc28" xlink:to="loc_srt_RangeMember_2459fd56-8312-4a53-9835-fa8a011a3e68" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_2a45be1d-4caa-4eaf-9a35-e25c388a7708" 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_2459fd56-8312-4a53-9835-fa8a011a3e68" xlink:to="loc_srt_MaximumMember_2a45be1d-4caa-4eaf-9a35-e25c388a7708" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_10fcb048-b97a-45ba-8e2f-14265c33f47f" 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_2459fd56-8312-4a53-9835-fa8a011a3e68" xlink:to="loc_srt_MinimumMember_10fcb048-b97a-45ba-8e2f-14265c33f47f" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsTableDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#LongTermObligationsTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsTableDetails" xlink:type="extended" id="iab819057e30744089913430edd0f2fa4_LongTermObligationsTableDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" 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_DebtInstrumentCarryingAmount_68e52ab5-1582-4c77-b094-733320e3def4" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_68e52ab5-1582-4c77-b094-733320e3def4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_03600ef4-b225-43aa-9585-65dd3623a458" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_03600ef4-b225-43aa-9585-65dd3623a458" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_5f030f65-6a08-4f56-9326-bb32a9109c14" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_5f030f65-6a08-4f56-9326-bb32a9109c14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_6a332f19-db54-4798-bb68-879f5f137038" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_6a332f19-db54-4798-bb68-879f5f137038" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_3a87b529-8683-44e6-bc20-a1f2278414ae" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtCurrent_3a87b529-8683-44e6-bc20-a1f2278414ae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_e5181fc4-abe0-44e0-869c-a5505c2e3786" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_e5181fc4-abe0-44e0-869c-a5505c2e3786" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_0f7fa3e9-cdea-4304-8073-852e42634435" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_0f7fa3e9-cdea-4304-8073-852e42634435" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_09f48637-839a-463b-9efc-099b4f3ae756" 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_ea326657-4a50-413b-a909-b3b41f12267a" xlink:to="loc_us-gaap_DebtInstrumentTable_09f48637-839a-463b-9efc-099b4f3ae756" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_c2ef0db2-d700-41da-b365-9cfa87c4088c" xlink:href="icui-20220630.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_09f48637-839a-463b-9efc-099b4f3ae756" xlink:to="loc_icui_TermLoanAxis_c2ef0db2-d700-41da-b365-9cfa87c4088c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_c2ef0db2-d700-41da-b365-9cfa87c4088c_default" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_c2ef0db2-d700-41da-b365-9cfa87c4088c" xlink:to="loc_icui_TermLoanDomain_c2ef0db2-d700-41da-b365-9cfa87c4088c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_1a60919a-7a2b-48e8-b83f-fba9f2f852e0" xlink:href="icui-20220630.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_c2ef0db2-d700-41da-b365-9cfa87c4088c" xlink:to="loc_icui_TermLoanDomain_1a60919a-7a2b-48e8-b83f-fba9f2f852e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_0609ccda-4e53-4c0b-a009-e4085ad95ed7" xlink:href="icui-20220630.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_1a60919a-7a2b-48e8-b83f-fba9f2f852e0" xlink:to="loc_icui_TermLoanAMember_0609ccda-4e53-4c0b-a009-e4085ad95ed7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_ffefffa2-19c8-4dd2-9b82-62de36cc9ad2" xlink:href="icui-20220630.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_1a60919a-7a2b-48e8-b83f-fba9f2f852e0" xlink:to="loc_icui_TermLoanBMember_ffefffa2-19c8-4dd2-9b82-62de36cc9ad2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_09f48637-839a-463b-9efc-099b4f3ae756" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ecea38ed-1813-4963-8495-c7f30bcb8ec0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_c3e1dd4b-ed6d-4c9a-9d54-08d91572d6b1" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ecea38ed-1813-4963-8495-c7f30bcb8ec0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_ea68c47b-d8c8-4a19-9c96-860b613d993b" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_ecea38ed-1813-4963-8495-c7f30bcb8ec0" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_ea68c47b-d8c8-4a19-9c96-860b613d993b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CommitmentsandContingenciesContingencyDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#CommitmentsandContingenciesContingencyDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CommitmentsandContingenciesContingencyDetails" xlink:type="extended" id="i18134945866c458e9ed268d6d44f624f_CommitmentsandContingenciesContingencyDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_a0db8b1a-74ce-483f-82a3-c4b3f9baee48" xlink:href="icui-20220630.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_icui_Contingentconsiderationgross_a0db8b1a-74ce-483f-82a3-c4b3f9baee48" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossST_efd21afa-bcb1-4855-8397-130124a0e765" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossST"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_icui_ContingentConsiderationGrossST_efd21afa-bcb1-4855-8397-130124a0e765" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossLT_5db7530b-0aa4-4dbb-a50a-202994bbfb88" xlink:href="icui-20220630.xsd#icui_ContingentConsiderationGrossLT"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_icui_ContingentConsiderationGrossLT_5db7530b-0aa4-4dbb-a50a-202994bbfb88" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_3c1edfd2-3982-4f7b-bc05-ef7ae658a397" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiability_3c1edfd2-3982-4f7b-bc05-ef7ae658a397" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_3a72e079-f4a3-4937-98f5-be26b270bf30" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_3a72e079-f4a3-4937-98f5-be26b270bf30" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_5c683317-b429-4877-a978-6c820dae2862" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_fe0e420b-0308-41d5-a5d0-afe61bd55de1" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_5c683317-b429-4877-a978-6c820dae2862" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_1767f18a-1fce-404f-b39b-f50a8e77547a" 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_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_5c683317-b429-4877-a978-6c820dae2862" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_1767f18a-1fce-404f-b39b-f50a8e77547a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1767f18a-1fce-404f-b39b-f50a8e77547a_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_1767f18a-1fce-404f-b39b-f50a8e77547a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_1767f18a-1fce-404f-b39b-f50a8e77547a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6e846880-2058-47aa-9ace-cd003bdd6f4a" 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_1767f18a-1fce-404f-b39b-f50a8e77547a" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6e846880-2058-47aa-9ace-cd003bdd6f4a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_d513d125-78b0-496f-a781-e36885e28029" xlink:href="icui-20220630.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6e846880-2058-47aa-9ace-cd003bdd6f4a" xlink:to="loc_icui_SmithsMedicalMember_d513d125-78b0-496f-a781-e36885e28029" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_412a0fd9-c0f9-4085-b1f7-01257d59d8a2" xlink:href="icui-20220630.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6e846880-2058-47aa-9ace-cd003bdd6f4a" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_412a0fd9-c0f9-4085-b1f7-01257d59d8a2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalDistributorMember_8a4327c1-f80e-4db7-b4d0-9fe865f0cee6" xlink:href="icui-20220630.xsd#icui_InternationalDistributorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6e846880-2058-47aa-9ace-cd003bdd6f4a" xlink:to="loc_icui_InternationalDistributorMember_8a4327c1-f80e-4db7-b4d0-9fe865f0cee6" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20220630.xsd#EquityAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended" id="i61d98d6eaadf4e6f8559661c85967ce0_EquityAccumulatedOtherComprehensiveIncomeLossDetails">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" 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_2bc2c8e6-a480-4073-a5bf-24a0f328d627" 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_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_2bc2c8e6-a480-4073-a5bf-24a0f328d627" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_bab0e1d5-690a-4c26-a980-7e4a7f1eac70" 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_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_bab0e1d5-690a-4c26-a980-7e4a7f1eac70" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_2768a117-8b5e-40dd-9c34-58b20fb7718a" 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_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_2768a117-8b5e-40dd-9c34-58b20fb7718a" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_f377260f-12d9-4d3c-aaea-2ed55bdc4411" 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_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_f377260f-12d9-4d3c-aaea-2ed55bdc4411" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_623b0306-8a0a-4a70-b5eb-8137b3de49f0" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_623b0306-8a0a-4a70-b5eb-8137b3de49f0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_eba07e69-aee8-4c26-9239-520a0f75e1ea" 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_b3d0a043-9696-4b7c-9f52-5911c7c0d9d4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_eba07e69-aee8-4c26-9239-520a0f75e1ea" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_20b0a092-0a41-4f61-84ca-14cf91c98062" 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_eba07e69-aee8-4c26-9239-520a0f75e1ea" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_20b0a092-0a41-4f61-84ca-14cf91c98062" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_20b0a092-0a41-4f61-84ca-14cf91c98062_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_20b0a092-0a41-4f61-84ca-14cf91c98062" xlink:to="loc_us-gaap_EquityComponentDomain_20b0a092-0a41-4f61-84ca-14cf91c98062_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_34143f7c-6cc1-4c39-b549-5e9c3a306a36" 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_20b0a092-0a41-4f61-84ca-14cf91c98062" xlink:to="loc_us-gaap_EquityComponentDomain_34143f7c-6cc1-4c39-b549-5e9c3a306a36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_a2955aaa-5b94-415a-97fa-4a67ed67fbbf" 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_34143f7c-6cc1-4c39-b549-5e9c3a306a36" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_a2955aaa-5b94-415a-97fa-4a67ed67fbbf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_67a840e2-22e8-428c-8119-84684d5a22da" 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_34143f7c-6cc1-4c39-b549-5e9c3a306a36" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_67a840e2-22e8-428c-8119-84684d5a22da" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_0eed7480-3d8f-43ee-a0d5-13e546d5cda5" 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_34143f7c-6cc1-4c39-b549-5e9c3a306a36" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_0eed7480-3d8f-43ee-a0d5-13e546d5cda5" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
