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

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2025 Workiva-->
<!--r:dafded61-f26b-462f-a997-b57b3bbc53c1,g:3ac98a7c-b5ac-4171-962f-ce0a8da552f5-->
<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-20250331.xsd#CondensedConsolidatedBalanceSheets"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_ac882dcb-98cd-496f-a4c2-a2ffd06efa82" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_9b535618-322e-4965-aff5-da34f771bc23" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_ac882dcb-98cd-496f-a4c2-a2ffd06efa82" xlink:to="loc_us-gaap_StatementTable_9b535618-322e-4965-aff5-da34f771bc23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_e9798a22-5825-4f6e-8610-273621bf7050" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9b535618-322e-4965-aff5-da34f771bc23" xlink:to="loc_srt_StatementScenarioAxis_e9798a22-5825-4f6e-8610-273621bf7050" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_e9798a22-5825-4f6e-8610-273621bf7050_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_e9798a22-5825-4f6e-8610-273621bf7050" xlink:to="loc_srt_ScenarioUnspecifiedDomain_e9798a22-5825-4f6e-8610-273621bf7050_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_fa973c4a-361e-41eb-99f1-b22c29aeafa2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_e9798a22-5825-4f6e-8610-273621bf7050" xlink:to="loc_srt_ScenarioUnspecifiedDomain_fa973c4a-361e-41eb-99f1-b22c29aeafa2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ac882dcb-98cd-496f-a4c2-a2ffd06efa82" xlink:to="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4fb0e59f-b185-4509-b3c5-bc1503c43e48" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_4fb0e59f-b185-4509-b3c5-bc1503c43e48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_b56acf89-a61c-4909-91ea-b04b313c6b44" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_b56acf89-a61c-4909-91ea-b04b313c6b44" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_2ce6ab68-98dd-49a5-b600-e46d591f8d57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsReceivableNetCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_2ce6ab68-98dd-49a5-b600-e46d591f8d57" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryNet_aa69c540-622d-428a-8ca6-7b7d6cb5a0eb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InventoryNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_InventoryNet_aa69c540-622d-428a-8ca6-7b7d6cb5a0eb" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidTaxes_d80e22e5-7a5f-4218-9c9e-0c55d45bb54a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidTaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_PrepaidTaxes_d80e22e5-7a5f-4218-9c9e-0c55d45bb54a" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_32c47207-c2da-45c5-ba16-0a4ef30fd30b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_32c47207-c2da-45c5-ba16-0a4ef30fd30b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_8c024db9-5bb1-4f56-86db-a2c504d96951" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_AssetsOfDisposalGroupIncludingDiscontinuedOperation_8c024db9-5bb1-4f56-86db-a2c504d96951" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsCurrent_df0f47f9-2bef-4710-9cc4-814b7b481918" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_341785dc-1106-41d8-bfa7-376e4240e68d" xlink:to="loc_us-gaap_AssetsCurrent_df0f47f9-2bef-4710-9cc4-814b7b481918" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_d44ec23b-ed4d-4a4f-835a-8d14f454c92d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_d44ec23b-ed4d-4a4f-835a-8d14f454c92d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_78e598fa-ca49-42b0-b57d-36be8bd90bcc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseRightOfUseAsset"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_78e598fa-ca49-42b0-b57d-36be8bd90bcc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_5247c3c7-8db1-497d-938d-c919891f7823" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_Goodwill_5247c3c7-8db1-497d-938d-c919891f7823" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_0f1bdd94-cd97-4564-8c84-78eb95a0d720" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_0f1bdd94-cd97-4564-8c84-78eb95a0d720" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_0f800318-893c-4241-aaae-c51384d07f60" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredIncomeTaxAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_0f800318-893c-4241-aaae-c51384d07f60" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_015cbe59-cec6-4e9f-b274-ce33fd2636d5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_015cbe59-cec6-4e9f-b274-ce33fd2636d5" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Assets_eac0cdde-31ee-4d31-8b19-7ce7b3d24dee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Assets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_1247484a-57c4-4d02-beb8-3a4311cfb3e9" xlink:to="loc_us-gaap_Assets_eac0cdde-31ee-4d31-8b19-7ce7b3d24dee" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_ac882dcb-98cd-496f-a4c2-a2ffd06efa82" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccountsPayableCurrent_f83c5fbb-88aa-44a2-9014-faca03615ecb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccountsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_AccountsPayableCurrent_f83c5fbb-88aa-44a2-9014-faca03615ecb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_ccfcd90c-9321-4788-a5f5-3be24a826570" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_ccfcd90c-9321-4788-a5f5-3be24a826570" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtCurrent_291e8a42-dd94-48e1-98d9-f07e0b6f3456" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_LongTermDebtCurrent_291e8a42-dd94-48e1-98d9-f07e0b6f3456" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_20d893bd-bb68-4f67-b620-630138ea44c9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedIncomeTaxesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_20d893bd-bb68-4f67-b620-630138ea44c9" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_326800ac-f1f1-43cb-b192-1f8b0b7d954c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_LiabilitiesOfDisposalGroupIncludingDiscontinuedOperation_326800ac-f1f1-43cb-b192-1f8b0b7d954c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrent_d1b70636-d721-4fbd-8dd3-e64f16c9d09a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_f4b83e3c-3e26-41e9-a104-fcad12753236" xlink:to="loc_us-gaap_LiabilitiesCurrent_d1b70636-d721-4fbd-8dd3-e64f16c9d09a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_b7c59bba-3476-432f-b3fb-be27cbdc8687" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_b7c59bba-3476-432f-b3fb-be27cbdc8687" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_b3051e8b-faa6-4691-ab82-39b56269dcac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherLiabilitiesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_b3051e8b-faa6-4691-ab82-39b56269dcac" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_c638a77d-138c-41af-8b18-1271036b420c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_c638a77d-138c-41af-8b18-1271036b420c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_7a209547-6620-4a58-8667-0f67b76fe014" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedIncomeTaxesNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_7a209547-6620-4a58-8667-0f67b76fe014" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommitmentsAndContingencies_35f0d457-664a-406c-b617-c6ce5d1d692b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommitmentsAndContingencies"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_CommitmentsAndContingencies_35f0d457-664a-406c-b617-c6ce5d1d692b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_a8904bd9-59b1-48bd-be51-9701f6625507" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_a8904bd9-59b1-48bd-be51-9701f6625507" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockValue_97de2d85-45a7-41dd-b87d-c106ea7e9256" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_CommonStockValue_97de2d85-45a7-41dd-b87d-c106ea7e9256" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d1e893b3-55ce-4851-9615-551020ed5a9c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_d1e893b3-55ce-4851-9615-551020ed5a9c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockValue_1dbd0225-bd1f-4f25-bf96-3b76489de4af" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_TreasuryStockValue_1dbd0225-bd1f-4f25-bf96-3b76489de4af" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1b3d8cc7-fb7b-40f8-8ba9-f076fd879b39" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsAccumulatedDeficit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_1b3d8cc7-fb7b-40f8-8ba9-f076fd879b39" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_18353d54-d1d7-436f-9d7d-6796bdcd7681" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_18353d54-d1d7-436f-9d7d-6796bdcd7681" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0a15ba3a-8433-4e94-ba06-65a563505a87" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_b3cec2c7-6516-4cbe-b756-16d6bc4466fd" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_0a15ba3a-8433-4e94-ba06-65a563505a87" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_36201dc6-c90a-4be2-9be5-f3d240d97831" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesAndStockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_3175e790-6af3-439e-9f37-a714dbfd80b0" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_36201dc6-c90a-4be2-9be5-f3d240d97831" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="simple" xlink:href="icui-20250331.xsd#CondensedConsolidatedStatementsofIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_9f1c0f0a-3f0b-4a4a-9088-cc1c77bf5835" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_StatementTable_9f1c0f0a-3f0b-4a4a-9088-cc1c77bf5835" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_82faece5-915b-49a1-ab2d-6c487a6272f9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_9f1c0f0a-3f0b-4a4a-9088-cc1c77bf5835" xlink:to="loc_srt_ProductOrServiceAxis_82faece5-915b-49a1-ab2d-6c487a6272f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_82faece5-915b-49a1-ab2d-6c487a6272f9_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_82faece5-915b-49a1-ab2d-6c487a6272f9" xlink:to="loc_srt_ProductsAndServicesDomain_82faece5-915b-49a1-ab2d-6c487a6272f9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_6df1b06a-2649-4545-8e3f-19af882d3624" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_82faece5-915b-49a1-ab2d-6c487a6272f9" xlink:to="loc_srt_ProductsAndServicesDomain_6df1b06a-2649-4545-8e3f-19af882d3624" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesAbstract_6a392119-e427-452e-b6ad-9c5342e6e9d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_RevenuesAbstract_6a392119-e427-452e-b6ad-9c5342e6e9d1" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b383e092-e4b8-461e-9b60-6eb1cbfe5b91" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_6a392119-e427-452e-b6ad-9c5342e6e9d1" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_b383e092-e4b8-461e-9b60-6eb1cbfe5b91" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfRevenue_eacb3840-a7ad-46da-a4ff-a7d55e3ab634" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_6a392119-e427-452e-b6ad-9c5342e6e9d1" xlink:to="loc_us-gaap_CostOfRevenue_eacb3840-a7ad-46da-a4ff-a7d55e3ab634" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GrossProfit_3bd1b1bf-216b-4c6a-ba8f-d362154996a4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GrossProfit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_6a392119-e427-452e-b6ad-9c5342e6e9d1" xlink:to="loc_us-gaap_GrossProfit_3bd1b1bf-216b-4c6a-ba8f-d362154996a4" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpensesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_a0ce76bd-407e-49a3-a48c-ef078922fc6f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_a0ce76bd-407e-49a3-a48c-ef078922fc6f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_601308b0-a823-45f7-9cc9-bb45b2add8c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_601308b0-a823-45f7-9cc9-bb45b2add8c7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Restructuringandstrategictransaction_9a8d2207-51ce-49f8-b6e9-d16da73b3402" xlink:href="icui-20250331.xsd#icui_Restructuringandstrategictransaction"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:to="loc_icui_Restructuringandstrategictransaction_9a8d2207-51ce-49f8-b6e9-d16da73b3402" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_71870533-feef-4c21-af1c-15761bf7c08a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_71870533-feef-4c21-af1c-15761bf7c08a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingExpenses_de17ec40-761f-4446-9142-9213c01e938c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingExpenses"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_00f94b0d-f7fe-4442-acf1-172a9f7b7983" xlink:to="loc_us-gaap_OperatingExpenses_de17ec40-761f-4446-9142-9213c01e938c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_a760fc2e-1c17-4efc-a365-1218ccdcf57e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_OperatingIncomeLoss_a760fc2e-1c17-4efc-a365-1218ccdcf57e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpense_118a7328-4a75-4d9c-8b63-b4c4cad96ea7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_InterestExpense_118a7328-4a75-4d9c-8b63-b4c4cad96ea7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_0222742e-b4bc-49ef-8648-1ebc50c05a4f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_0222742e-b4bc-49ef-8648-1ebc50c05a4f" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_50d2983e-036c-4eb5-aeb6-f11b674280b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_50d2983e-036c-4eb5-aeb6-f11b674280b8" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_3b32da3b-b056-4d05-af36-2ab942f7cf1a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_3b32da3b-b056-4d05-af36-2ab942f7cf1a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_83a9f7ab-8b94-4912-895a-d2ff1de643cc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_ProfitLoss_83a9f7ab-8b94-4912-895a-d2ff1de643cc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareAbstract_9b29ec2e-2ad3-4058-a3a4-4b36fa5ef749" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_EarningsPerShareAbstract_9b29ec2e-2ad3-4058-a3a4-4b36fa5ef749" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareBasic_ec7e33e2-9194-4e6f-b526-74c07bb2900b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_9b29ec2e-2ad3-4058-a3a4-4b36fa5ef749" xlink:to="loc_us-gaap_EarningsPerShareBasic_ec7e33e2-9194-4e6f-b526-74c07bb2900b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarningsPerShareDiluted_959d94b6-d42d-48ae-863b-c763dce7f7b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarningsPerShareDiluted"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_9b29ec2e-2ad3-4058-a3a4-4b36fa5ef749" xlink:to="loc_us-gaap_EarningsPerShareDiluted_959d94b6-d42d-48ae-863b-c763dce7f7b0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_0c1126ea-74bd-4a8e-94e7-27daf447b51d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_aab63abd-fec5-4481-8721-7ba089991e51" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_0c1126ea-74bd-4a8e-94e7-27daf447b51d" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_5b9edbf8-3175-4f91-92d2-3d71af58ea13" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_0c1126ea-74bd-4a8e-94e7-27daf447b51d" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_5b9edbf8-3175-4f91-92d2-3d71af58ea13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_cabe162a-31cd-4de8-be7f-620a5932f3cd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_0c1126ea-74bd-4a8e-94e7-27daf447b51d" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_cabe162a-31cd-4de8-be7f-620a5932f3cd" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="simple" xlink:href="icui-20250331.xsd#CondensedConsolidatedStatementsofComprehensiveIncome"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_109361a2-951f-45da-8a1d-91cebed17cd1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_614d6adb-bbc8-403d-8f75-b5c4683a1c72" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_109361a2-951f-45da-8a1d-91cebed17cd1" xlink:to="loc_us-gaap_StatementTable_614d6adb-bbc8-403d-8f75-b5c4683a1c72" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_614d6adb-bbc8-403d-8f75-b5c4683a1c72" xlink:to="loc_srt_StatementScenarioAxis_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea" xlink:to="loc_srt_ScenarioUnspecifiedDomain_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_47670684-8d51-401b-9699-b3f15a57c5cc" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_006ebff8-83c0-4ce9-9d80-cd80bf3cf8ea" xlink:to="loc_srt_ScenarioUnspecifiedDomain_47670684-8d51-401b-9699-b3f15a57c5cc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_7159cd80-edd8-4162-965c-71c7dde5151a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_109361a2-951f-45da-8a1d-91cebed17cd1" xlink:to="loc_us-gaap_ProfitLoss_7159cd80-edd8-4162-965c-71c7dde5151a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_a8a47bb8-6123-4b68-a986-1cdcb4db67ca" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_109361a2-951f-45da-8a1d-91cebed17cd1" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_a8a47bb8-6123-4b68-a986-1cdcb4db67ca" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_b8807a95-ef20-4461-8af4-b47ad46ed342" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_a8a47bb8-6123-4b68-a986-1cdcb4db67ca" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_b8807a95-ef20-4461-8af4-b47ad46ed342" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_fec0d4ea-c67b-433f-9dd1-ca5885399fde" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_a8a47bb8-6123-4b68-a986-1cdcb4db67ca" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_fec0d4ea-c67b-433f-9dd1-ca5885399fde" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_93d42988-4d0e-4e48-be33-68b0b63826c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_a8a47bb8-6123-4b68-a986-1cdcb4db67ca" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_93d42988-4d0e-4e48-be33-68b0b63826c7" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_cadd7ff6-8dd8-4a77-84dd-c22b4efd485f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ComprehensiveIncomeNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_109361a2-951f-45da-8a1d-91cebed17cd1" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_cadd7ff6-8dd8-4a77-84dd-c22b4efd485f" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofStockholdersEquityStatement" xlink:type="simple" xlink:href="icui-20250331.xsd#CondensedConsolidatedStatementsofStockholdersEquityStatement"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofStockholdersEquityStatement" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_6ffdd3d5-89dc-4e53-970d-f3bebb0cbbcd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_8ce5c1a1-3002-43c7-a805-63a77ddda15d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6ffdd3d5-89dc-4e53-970d-f3bebb0cbbcd" xlink:to="loc_us-gaap_StatementTable_8ce5c1a1-3002-43c7-a805-63a77ddda15d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_8ce5c1a1-3002-43c7-a805-63a77ddda15d" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9" xlink:to="loc_us-gaap_EquityComponentDomain_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_bf4eec0e-b9c5-4b68-bdb1-9dbad6742ac9" xlink:to="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CommonStockSharesMember_8888cf99-a3cd-4a84-9652-34f13eab9c3c" xlink:href="icui-20250331.xsd#icui_CommonStockSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_icui_CommonStockSharesMember_8888cf99-a3cd-4a84-9652-34f13eab9c3c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_56e1de39-b670-46aa-a977-047583d07b90" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_us-gaap_CommonStockMember_56e1de39-b670-46aa-a977-047583d07b90" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_3ddf85be-95bb-4fbc-a8e5-1cec8bc30531" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_3ddf85be-95bb-4fbc-a8e5-1cec8bc30531" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TreasuryStockCommonMember_ed906e15-703d-455c-a6c5-a81c719891b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TreasuryStockCommonMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_us-gaap_TreasuryStockCommonMember_ed906e15-703d-455c-a6c5-a81c719891b2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_61dd75ef-073c-47ff-aaed-d876d6c50ac4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_us-gaap_RetainedEarningsMember_61dd75ef-073c-47ff-aaed-d876d6c50ac4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_fdf466f8-8e0f-45be-aace-33381bbb1d01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_84e64066-d980-4685-a4ac-5f745108a8e0" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_fdf466f8-8e0f-45be-aace-33381bbb1d01" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6ffdd3d5-89dc-4e53-970d-f3bebb0cbbcd" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_3e16e49e-0da7-44f1-a582-f9e427e3e3b0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_CommonStockSharesIssued_3e16e49e-0da7-44f1-a582-f9e427e3e3b0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e32737b6-fed5-447a-99b6-c534cee3d04f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_e32737b6-fed5-447a-99b6-c534cee3d04f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d5861ae6-0ffb-4d66-a6c4-09cc6f20a933" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_d5861ae6-0ffb-4d66-a6c4-09cc6f20a933" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockSharesIssued_e0286030-be73-40c6-b9a4-13e8f502ccc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockSharesIssued"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_4aa74cc8-efd0-474e-859f-992c1873355c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_StockholdersEquity_4aa74cc8-efd0-474e-859f-992c1873355c" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_38b25b32-6da0-40f8-9d38-77004007167d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_38b25b32-6da0-40f8-9d38-77004007167d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_7cdaf0c6-e224-466b-b5ae-195fd0985c99" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_7cdaf0c6-e224-466b-b5ae-195fd0985c99" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_89000254-be8a-434a-9018-6383caaee8b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_89000254-be8a-434a-9018-6383caaee8b9" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_6cb791e8-257b-4a14-b572-6be9c413b9b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalOther"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_6cb791e8-257b-4a14-b572-6be9c413b9b1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0746eec1-4842-45b4-969c-917bc82509b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_0746eec1-4842-45b4-969c-917bc82509b8" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_d99e3171-3513-4e52-942e-fafa395630ba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_d99e3171-3513-4e52-942e-fafa395630ba" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_39551149-f224-4151-b1af-358a1ba71cc2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_0997f62b-9805-4c22-ac74-02dc49b60a11" xlink:to="loc_us-gaap_NetIncomeLoss_39551149-f224-4151-b1af-358a1ba71cc2" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquity_adf7df9f-9c2a-48a8-9181-3aa3ad72cb75" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquity"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="simple" xlink:href="icui-20250331.xsd#CondensedConsolidatedStatementsofCashFlows"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsofCashFlows" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_2e28aca7-da4a-4dc5-ac87-f5f535eb2a27" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_StatementTable_2e28aca7-da4a-4dc5-ac87-f5f535eb2a27" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementScenarioAxis_cbd80bc2-543e-4621-8da0-1aad5884168d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementScenarioAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2e28aca7-da4a-4dc5-ac87-f5f535eb2a27" xlink:to="loc_srt_StatementScenarioAxis_cbd80bc2-543e-4621-8da0-1aad5884168d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_cbd80bc2-543e-4621-8da0-1aad5884168d_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_cbd80bc2-543e-4621-8da0-1aad5884168d" xlink:to="loc_srt_ScenarioUnspecifiedDomain_cbd80bc2-543e-4621-8da0-1aad5884168d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScenarioUnspecifiedDomain_8b0711ca-f172-4278-8ea7-fc8d9a0292ec" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScenarioUnspecifiedDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_cbd80bc2-543e-4621-8da0-1aad5884168d" xlink:to="loc_srt_ScenarioUnspecifiedDomain_8b0711ca-f172-4278-8ea7-fc8d9a0292ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectAbstract_e090177c-053f-47bc-b91e-7a623099d44c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectAbstract_e090177c-053f-47bc-b91e-7a623099d44c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_846b3c5c-4c86-4542-a0f6-76bfef0b73f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectAbstract_e090177c-053f-47bc-b91e-7a623099d44c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_846b3c5c-4c86-4542-a0f6-76bfef0b73f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_846b3c5c-4c86-4542-a0f6-76bfef0b73f9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_53a1e6d5-5850-4acd-ab40-96685078dad3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_ProfitLoss_53a1e6d5-5850-4acd-ab40-96685078dad3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_124c23f0-c5d7-45b7-b152-6600980180a4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DepreciationDepletionAndAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_124c23f0-c5d7-45b7-b152-6600980180a4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_08bb469a-7fee-4887-8230-0539650d2e80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAssetAmortizationExpense_08bb469a-7fee-4887-8230-0539650d2e80" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_8e053702-e626-4a95-938f-cd6b85f2276c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProvisionForDoubtfulAccounts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_8e053702-e626-4a95-938f-cd6b85f2276c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ProvisionForWarrantyAndReturns_c7d498b7-45fa-4760-9122-8285bdbfd598" xlink:href="icui-20250331.xsd#icui_ProvisionForWarrantyAndReturns"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_icui_ProvisionForWarrantyAndReturns_c7d498b7-45fa-4760-9122-8285bdbfd598" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_4144e621-dfcb-4633-b0e2-9e67a56b055b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_ShareBasedCompensation_4144e621-dfcb-4633-b0e2-9e67a56b055b" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_7ec5dfc8-7ce7-4be5-a363-7bf94c70f3dd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_7ec5dfc8-7ce7-4be5-a363-7bf94c70f3dd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_16a7a90d-0152-4ee7-9b79-c14566985adb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfFinancingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_16a7a90d-0152-4ee7-9b79-c14566985adb" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_213e53f3-f366-4868-9e72-790ee2b9e6c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_213e53f3-f366-4868-9e72-790ee2b9e6c7" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Sparepartsusage_6ed092b8-32e6-44e3-9da6-448a858b156c" xlink:href="icui-20250331.xsd#icui_Sparepartsusage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_icui_Sparepartsusage_6ed092b8-32e6-44e3-9da6-448a858b156c" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_6cdf623b-ffa2-4236-9c5e-836fc17a2e4d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNoncashIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_6cdf623b-ffa2-4236-9c5e-836fc17a2e4d" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_fb6a01a1-06c6-40be-a450-a8afe261fa55" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_fb6a01a1-06c6-40be-a450-a8afe261fa55" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_abc70232-77e0-4c8a-b086-3b429d38c2e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInInventories"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_abc70232-77e0-4c8a-b086-3b429d38c2e6" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_a1c02ad5-373a-4a44-9449-c95d2b6b4172" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_a1c02ad5-373a-4a44-9449-c95d2b6b4172" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_780c7d3d-f964-4106-b5ae-07556cba4de9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_780c7d3d-f964-4106-b5ae-07556cba4de9" xlink:type="arc" order="15"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_cd9538e3-e1d9-4c12-b30b-c0304e13e8f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInAccountsPayable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_cd9538e3-e1d9-4c12-b30b-c0304e13e8f3" xlink:type="arc" order="16"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_bfe1564b-2ae5-4345-b828-cd2c9de5d227" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_bfe1564b-2ae5-4345-b828-cd2c9de5d227" xlink:type="arc" order="17"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_781ac207-f21f-4704-a438-ec0051cf4b5c" xlink:href="icui-20250331.xsd#icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_781ac207-f21f-4704-a438-ec0051cf4b5c" xlink:type="arc" order="18"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_752b3415-7936-4a90-8c63-c7f151c4b21f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_7beef659-abf5-42a3-aeae-fa7e334c062f" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_752b3415-7936-4a90-8c63-c7f151c4b21f" xlink:type="arc" order="19"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_846b3c5c-4c86-4542-a0f6-76bfef0b73f9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_a0f7cd0a-2e65-4815-bc4b-73edd9acf7ea" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_a0f7cd0a-2e65-4815-bc4b-73edd9acf7ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_53f1fa5b-e558-4c12-9398-758a37515f90" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_53f1fa5b-e558-4c12-9398-758a37515f90" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_c0028fa1-0b0d-43cc-b9d3-d56589379d11" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsToAcquireIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_c0028fa1-0b0d-43cc-b9d3-d56589379d11" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_03f1ce88-0b98-4cd1-a82a-0b56662b9144" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_03f1ce88-0b98-4cd1-a82a-0b56662b9144" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_e2208bc2-3d1b-4b95-a66b-0f00bf1b7b7d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_d211a67b-d2ea-423f-a097-96aad9631bf0" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_e2208bc2-3d1b-4b95-a66b-0f00bf1b7b7d" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseExcludingExchangeRateEffectAbstract_846b3c5c-4c86-4542-a0f6-76bfef0b73f9" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_373bab36-5748-4b1f-9adc-6a43a6616759" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_373bab36-5748-4b1f-9adc-6a43a6616759" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_415a0427-a757-4cff-8cdf-f98622863149" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_415a0427-a757-4cff-8cdf-f98622863149" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinanceLeasePrincipalPayments_59d7e56b-a996-4231-9023-606f33199c7a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinanceLeasePrincipalPayments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_FinanceLeasePrincipalPayments_59d7e56b-a996-4231-9023-606f33199c7a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_692cf820-88a8-4311-91f7-fe8b1629d928" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_PaymentForContingentConsiderationLiabilityFinancingActivities_692cf820-88a8-4311-91f7-fe8b1629d928" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_78f8080f-ab01-4110-b88e-710fa049a1df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_78f8080f-ab01-4110-b88e-710fa049a1df" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_0fe96c69-b05f-44e4-a553-126276a92d9a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_ffbaa91d-cb0a-4e37-bd31-473c024b6907" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_0fe96c69-b05f-44e4-a553-126276a92d9a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_206d670e-d37f-42ec-a119-df467a5d19f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffectAbstract_e090177c-053f-47bc-b91e-7a623099d44c" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_206d670e-d37f-42ec-a119-df467a5d19f8" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_31fdc2ff-36ee-4c31-823a-862fe5f86153" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsIncludingDisposalGroupAndDiscontinuedOperationsAbstract_206d670e-d37f-42ec-a119-df467a5d19f8" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_31fdc2ff-36ee-4c31-823a-862fe5f86153" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_96f4410d-9391-41b4-82d5-047d10c82a32" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_96f4410d-9391-41b4-82d5-047d10c82a32" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_8386ba3c-bdcc-4bb8-82aa-98c6c63234aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_8386ba3c-bdcc-4bb8-82aa-98c6c63234aa" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SupplementalCashFlowInformationAbstract_b90c4e41-4f21-40f7-bd81-6c2770967d85" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SupplementalCashFlowInformationAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_SupplementalCashFlowInformationAbstract_b90c4e41-4f21-40f7-bd81-6c2770967d85" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_a67c29ee-716b-46af-8a3b-c598bfcb2914" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SupplementalCashFlowInformationAbstract_b90c4e41-4f21-40f7-bd81-6c2770967d85" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_a67c29ee-716b-46af-8a3b-c598bfcb2914" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_90e9ce58-c7c6-4d21-9924-6bbbb503af1c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_e5705809-a785-4e06-89dd-5579fbfc322c" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_90e9ce58-c7c6-4d21-9924-6bbbb503af1c" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationLiabilityDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#RestructuringStrategicTransactionandIntegrationLiabilityDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionandIntegrationLiabilityDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_a1811fe5-9f13-4016-9474-78acecd6c3de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_a1811fe5-9f13-4016-9474-78acecd6c3de" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_a1811fe5-9f13-4016-9474-78acecd6c3de" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_5e2dbd0e-5528-401c-aaf3-9b32428826d9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_5b689f4c-bfe5-4b40-a8fe-e73c3b70e1ab" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_5e2dbd0e-5528-401c-aaf3-9b32428826d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EmployeeSeveranceMember_8280a0e0-26d1-45b3-a54e-a2b097525184" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EmployeeSeveranceMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_5e2dbd0e-5528-401c-aaf3-9b32428826d9" xlink:to="loc_us-gaap_EmployeeSeveranceMember_8280a0e0-26d1-45b3-a54e-a2b097525184" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FacilityClosingMember_da2658df-733f-4053-b14f-a96e3de6ab3a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FacilityClosingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_5e2dbd0e-5528-401c-aaf3-9b32428826d9" xlink:to="loc_us-gaap_FacilityClosingMember_da2658df-733f-4053-b14f-a96e3de6ab3a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_2c44485b-3422-4f42-9901-431482f25118" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserve"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_RestructuringReserve_2c44485b-3422-4f42-9901-431482f25118" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_ed6afb34-403a-48d3-9071-daab534ef9bc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_RestructuringCharges_ed6afb34-403a-48d3-9071-daab534ef9bc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForRestructuring_1b0d2c0b-961f-48d8-bc0a-cb5bdb6259da" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsForRestructuring"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_PaymentsForRestructuring_1b0d2c0b-961f-48d8-bc0a-cb5bdb6259da" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveAccrualAdjustment1_1b3e5bc8-932e-476e-b2a4-e143b206ecdb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserveAccrualAdjustment1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_RestructuringReserveAccrualAdjustment1_1b3e5bc8-932e-476e-b2a4-e143b206ecdb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserveTranslationAdjustment_019fe945-ceda-4c73-9c82-357543a56707" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserveTranslationAdjustment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_46524634-6c10-4c0b-979e-fd7a66a2caaa" xlink:to="loc_us-gaap_RestructuringReserveTranslationAdjustment_019fe945-ceda-4c73-9c82-357543a56707" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringReserve_6f1fc3ff-158f-4bda-876d-3ee9d4cfc958" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringReserve"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyProductLineDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#RevenueDisaggregatedRevenuebyProductLineDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyProductLineDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_d4aef774-19f7-453a-81a9-127345f58217" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_5c60f28b-f3b9-4486-97c3-02ccbec751b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d4aef774-19f7-453a-81a9-127345f58217" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_5c60f28b-f3b9-4486-97c3-02ccbec751b8" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_56f73704-5db2-4db5-a44d-4cc79e914de7" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_5c60f28b-f3b9-4486-97c3-02ccbec751b8" xlink:to="loc_srt_ProductOrServiceAxis_56f73704-5db2-4db5-a44d-4cc79e914de7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_56f73704-5db2-4db5-a44d-4cc79e914de7_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_56f73704-5db2-4db5-a44d-4cc79e914de7" xlink:to="loc_srt_ProductsAndServicesDomain_56f73704-5db2-4db5-a44d-4cc79e914de7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_520dd555-80f4-484f-955f-84d8547fa99d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_56f73704-5db2-4db5-a44d-4cc79e914de7" xlink:to="loc_srt_ProductsAndServicesDomain_520dd555-80f4-484f-955f-84d8547fa99d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionConsumablesMember_66992912-d7fc-4710-ba11-aa20e18d5d50" xlink:href="icui-20250331.xsd#icui_InfusionConsumablesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_520dd555-80f4-484f-955f-84d8547fa99d" xlink:to="loc_icui_InfusionConsumablesMember_66992912-d7fc-4710-ba11-aa20e18d5d50" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InfusionSystemsMember_2019e77f-ce1a-45ae-8707-1be3ee2e4c15" xlink:href="icui-20250331.xsd#icui_InfusionSystemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_520dd555-80f4-484f-955f-84d8547fa99d" xlink:to="loc_icui_InfusionSystemsMember_2019e77f-ce1a-45ae-8707-1be3ee2e4c15" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_VitalCareMember_267e38db-b4ed-4512-9b46-bbe7e03d76b9" xlink:href="icui-20250331.xsd#icui_VitalCareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_520dd555-80f4-484f-955f-84d8547fa99d" xlink:to="loc_icui_VitalCareMember_267e38db-b4ed-4512-9b46-bbe7e03d76b9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_89f0cfc0-706d-413c-beda-bc9740aed39b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_d4aef774-19f7-453a-81a9-127345f58217" xlink:to="loc_us-gaap_Revenues_89f0cfc0-706d-413c-beda-bc9740aed39b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyGeographyDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#RevenueDisaggregatedRevenuebyGeographyDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenuebyGeographyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_5ec26520-439f-4015-ae1b-43361bde455a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_520be9df-f2ce-48c5-a10a-3a852a43c116" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5ec26520-439f-4015-ae1b-43361bde455a" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_520be9df-f2ce-48c5-a10a-3a852a43c116" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_0610b49b-870d-4091-8f93-4abae7eac4f6" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_520be9df-f2ce-48c5-a10a-3a852a43c116" xlink:to="loc_srt_StatementGeographicalAxis_0610b49b-870d-4091-8f93-4abae7eac4f6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_0610b49b-870d-4091-8f93-4abae7eac4f6_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_0610b49b-870d-4091-8f93-4abae7eac4f6" xlink:to="loc_srt_SegmentGeographicalDomain_0610b49b-870d-4091-8f93-4abae7eac4f6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_0610b49b-870d-4091-8f93-4abae7eac4f6" xlink:to="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_882e9b42-8523-44be-bef2-a25dc26448fe" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:to="loc_country_US_882e9b42-8523-44be-bef2-a25dc26448fe" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EMEAMember_a839c039-ace7-42e8-a41f-07accf197506" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EMEAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:to="loc_us-gaap_EMEAMember_a839c039-ace7-42e8-a41f-07accf197506" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_278de11a-57a0-41b5-ae5b-56c8cf03871b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:to="loc_srt_AsiaPacificMember_278de11a-57a0-41b5-ae5b-56c8cf03871b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherforeigncountriesMember_88d37a1f-589b-4656-9eb2-61d5e8f261cd" xlink:href="icui-20250331.xsd#icui_OtherforeigncountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_ed893636-75fa-4455-a897-b462d71f86b1" xlink:to="loc_icui_OtherforeigncountriesMember_88d37a1f-589b-4656-9eb2-61d5e8f261cd" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_7c8abace-5f2c-4243-bca9-02d6c67db827" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_5ec26520-439f-4015-ae1b-43361bde455a" xlink:to="loc_us-gaap_Revenues_7c8abace-5f2c-4243-bca9-02d6c67db827" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#RevenueContractLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:href="icui-20250331.xsd#icui_ContractassetandliabilitybalancesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContractassetandliabilitybalancesTable_4e392062-8695-4fd0-b667-d2c3acebe6e6" xlink:href="icui-20250331.xsd#icui_ContractassetandliabilitybalancesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:to="loc_icui_ContractassetandliabilitybalancesTable_4e392062-8695-4fd0-b667-d2c3acebe6e6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_07a011e4-5105-4997-bed8-2d0e97f6cb5d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ContractassetandliabilitybalancesTable_4e392062-8695-4fd0-b667-d2c3acebe6e6" xlink:to="loc_srt_ProductOrServiceAxis_07a011e4-5105-4997-bed8-2d0e97f6cb5d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_07a011e4-5105-4997-bed8-2d0e97f6cb5d_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_07a011e4-5105-4997-bed8-2d0e97f6cb5d" xlink:to="loc_srt_ProductsAndServicesDomain_07a011e4-5105-4997-bed8-2d0e97f6cb5d_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_07a011e4-5105-4997-bed8-2d0e97f6cb5d" xlink:to="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_7d6ee2cf-af7e-4ea0-847c-871d12a66707" xlink:href="icui-20250331.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:to="loc_icui_EquipmentrevenueMember_7d6ee2cf-af7e-4ea0-847c-871d12a66707" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_5ba05e24-f351-4691-8c82-fe90b535a317" xlink:href="icui-20250331.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:to="loc_icui_SoftwarerevenueMember_5ba05e24-f351-4691-8c82-fe90b535a317" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GovernmentGrantRevenueMember_962f0e17-d61e-4cce-a4d2-c85b3adbe61b" xlink:href="icui-20250331.xsd#icui_GovernmentGrantRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:to="loc_icui_GovernmentGrantRevenueMember_962f0e17-d61e-4cce-a4d2-c85b3adbe61b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherDeferredRevenueMember_7804bde0-fb96-4896-876d-3d9ea3169d91" xlink:href="icui-20250331.xsd#icui_OtherDeferredRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_35c9a75f-5cf2-4a86-8f70-186bbaa6a8d9" xlink:to="loc_icui_OtherDeferredRevenueMember_7804bde0-fb96-4896-876d-3d9ea3169d91" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MovementInDeferredRevenueRollForward_df15d04f-9642-4788-8338-73eab02beed6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MovementInDeferredRevenueRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:to="loc_us-gaap_MovementInDeferredRevenueRollForward_df15d04f-9642-4788-8338-73eab02beed6" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_0b14eee9-012b-45f8-80f8-f6b68135ecdc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiability"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:to="loc_us-gaap_ContractWithCustomerLiability_0b14eee9-012b-45f8-80f8-f6b68135ecdc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_4a271090-58d7-4cb8-8399-6afebe55d72e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_4a271090-58d7-4cb8-8399-6afebe55d72e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredRevenueAdditions_4bf69110-d0c7-4a05-b6c3-1ca58fdf791f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredRevenueAdditions"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_7406f500-b194-49d1-8ba7-0699a7aa0dc6" xlink:to="loc_us-gaap_DeferredRevenueAdditions_4bf69110-d0c7-4a05-b6c3-1ca58fdf791f" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContractWithCustomerLiability_1efb65a7-c3f8-4ccc-8abc-2b3993429009" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContractWithCustomerLiability"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDeferredRevenuebyArrangementDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#RevenueDeferredRevenuebyArrangementDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDeferredRevenuebyArrangementDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_94e0987a-b278-48b4-a47c-857e3326e271" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_cd62f4ca-fab1-4173-b777-a348c7a47126" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_94e0987a-b278-48b4-a47c-857e3326e271" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_cd62f4ca-fab1-4173-b777-a348c7a47126" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11" xlink:href="icui-20250331.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_cd62f4ca-fab1-4173-b777-a348c7a47126" xlink:to="loc_icui_TimingAxis_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11_default" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11" xlink:to="loc_icui_TimingDomain_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_16a7c7b1-7127-4817-b9fe-436b6324cfc7" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_f0ae9cd0-d6f9-4df0-897c-4e25d5777c11" xlink:to="loc_icui_TimingDomain_16a7c7b1-7127-4817-b9fe-436b6324cfc7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermMember_c66cc5ac-1e40-416a-9209-389ce9c024aa" xlink:href="icui-20250331.xsd#icui_ShortTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_16a7c7b1-7127-4817-b9fe-436b6324cfc7" xlink:to="loc_icui_ShortTermMember_c66cc5ac-1e40-416a-9209-389ce9c024aa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermMember_ac9b2081-f624-47ea-8450-d26e28175f4e" xlink:href="icui-20250331.xsd#icui_LongTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_16a7c7b1-7127-4817-b9fe-436b6324cfc7" xlink:to="loc_icui_LongTermMember_ac9b2081-f624-47ea-8450-d26e28175f4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductOrServiceAxis_008b7d15-16cc-4423-aa58-11df1cd479cd" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductOrServiceAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_cd62f4ca-fab1-4173-b777-a348c7a47126" xlink:to="loc_srt_ProductOrServiceAxis_008b7d15-16cc-4423-aa58-11df1cd479cd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_008b7d15-16cc-4423-aa58-11df1cd479cd_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_008b7d15-16cc-4423-aa58-11df1cd479cd" xlink:to="loc_srt_ProductsAndServicesDomain_008b7d15-16cc-4423-aa58-11df1cd479cd_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ProductsAndServicesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_008b7d15-16cc-4423-aa58-11df1cd479cd" xlink:to="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_EquipmentrevenueMember_2ba63931-0a45-4b38-aa34-fb0c58f0941f" xlink:href="icui-20250331.xsd#icui_EquipmentrevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:to="loc_icui_EquipmentrevenueMember_2ba63931-0a45-4b38-aa34-fb0c58f0941f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SoftwarerevenueMember_77c4f03e-0410-4cd6-80b7-84641561668e" xlink:href="icui-20250331.xsd#icui_SoftwarerevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:to="loc_icui_SoftwarerevenueMember_77c4f03e-0410-4cd6-80b7-84641561668e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GovernmentGrantRevenueMember_b81054e9-bac8-4299-bcc8-9cdd5ff110c6" xlink:href="icui-20250331.xsd#icui_GovernmentGrantRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:to="loc_icui_GovernmentGrantRevenueMember_b81054e9-bac8-4299-bcc8-9cdd5ff110c6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherDeferredRevenueMember_b20da9f9-9c97-43ca-b023-4d74b1d52c08" xlink:href="icui-20250331.xsd#icui_OtherDeferredRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_8c26a160-6430-4f43-b997-c0bd837ef0bb" xlink:to="loc_icui_OtherDeferredRevenueMember_b20da9f9-9c97-43ca-b023-4d74b1d52c08" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_d0dd2a13-a9e8-4d41-beb6-5ef914743d13" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_94e0987a-b278-48b4-a47c-857e3326e271" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_d0dd2a13-a9e8-4d41-beb6-5ef914743d13" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesTextDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#LeasesTextDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesTextDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_8289ddb5-7647-4031-898a-d30d727d8aeb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_e3b02390-6fcf-4088-97ed-d02472586f46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeLeaseDescriptionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8289ddb5-7647-4031-898a-d30d727d8aeb" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_e3b02390-6fcf-4088-97ed-d02472586f46" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_e50a4e07-f248-460a-9dc5-e0783af0435b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_e3b02390-6fcf-4088-97ed-d02472586f46" xlink:to="loc_srt_RangeAxis_e50a4e07-f248-460a-9dc5-e0783af0435b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_e50a4e07-f248-460a-9dc5-e0783af0435b_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_e50a4e07-f248-460a-9dc5-e0783af0435b" xlink:to="loc_srt_RangeMember_e50a4e07-f248-460a-9dc5-e0783af0435b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_61984dd6-c220-4c54-9430-3c9cde9c886e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_e50a4e07-f248-460a-9dc5-e0783af0435b" xlink:to="loc_srt_RangeMember_61984dd6-c220-4c54-9430-3c9cde9c886e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_5077b5d4-dacf-4b89-9c18-5b9edb917a3a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_61984dd6-c220-4c54-9430-3c9cde9c886e" xlink:to="loc_srt_MinimumMember_5077b5d4-dacf-4b89-9c18-5b9edb917a3a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ad9c54aa-2fa1-482e-940e-8e4ffbc5ab40" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_61984dd6-c220-4c54-9430-3c9cde9c886e" xlink:to="loc_srt_MaximumMember_ad9c54aa-2fa1-482e-940e-8e4ffbc5ab40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_868cc23a-00c0-4342-ba51-8a796204ad92" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LesseeOperatingLeaseTermOfContract"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8289ddb5-7647-4031-898a-d30d727d8aeb" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_868cc23a-00c0-4342-ba51-8a796204ad92" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Optiontoextendinyears_eab309bd-4d97-4a4d-a972-3f3cd2cb1c1e" xlink:href="icui-20250331.xsd#icui_Optiontoextendinyears"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_8289ddb5-7647-4031-898a-d30d727d8aeb" xlink:to="loc_icui_Optiontoextendinyears_eab309bd-4d97-4a4d-a972-3f3cd2cb1c1e" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsForeignExchangeForwardContractsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_54ddc638-5b73-4fa1-ba46-8c9747adc2d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_2caa634a-25b8-4286-b2a1-88354f99c672" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_54ddc638-5b73-4fa1-ba46-8c9747adc2d3" xlink:to="loc_us-gaap_DerivativeTable_2caa634a-25b8-4286-b2a1-88354f99c672" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CurrencyAxis_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_CurrencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_2caa634a-25b8-4286-b2a1-88354f99c672" xlink:to="loc_srt_CurrencyAxis_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e_default" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CurrencyAxis_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e" xlink:to="loc_currency_AllCurrenciesDomain_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_AllCurrenciesDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CurrencyAxis_6fcd3dfc-e0fa-4ec6-a3c5-31850d8f846e" xlink:to="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_CAD_88e9695d-b428-410a-8d05-c6d7b2163914" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_CAD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:to="loc_currency_CAD_88e9695d-b428-410a-8d05-c6d7b2163914" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_AUD_5fff83dc-e2ec-46cb-a558-a4888140c258" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_AUD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:to="loc_currency_AUD_5fff83dc-e2ec-46cb-a558-a4888140c258" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_USD_e636b266-ff90-4cc5-b2fd-171458fe1709" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_USD"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:to="loc_currency_USD_e636b266-ff90-4cc5-b2fd-171458fe1709" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_currency_MXN_d5d0abaf-c3b3-40e9-85f4-c92857a27f9a" xlink:href="https://xbrl.sec.gov/currency/2024/currency-2024.xsd#currency_MXN"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_currency_AllCurrenciesDomain_eb9396b7-e5ba-4233-b1ca-a6b68e7f48d4" xlink:to="loc_currency_MXN_d5d0abaf-c3b3-40e9-85f4-c92857a27f9a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisAxis_3a95c517-eee2-4b2e-9ed8-c956f9269dad" xlink:href="icui-20250331.xsd#icui_Srt_MultipleCurrencyAxisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_2caa634a-25b8-4286-b2a1-88354f99c672" xlink:to="loc_icui_Srt_MultipleCurrencyAxisAxis_3a95c517-eee2-4b2e-9ed8-c956f9269dad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisDomain_3a95c517-eee2-4b2e-9ed8-c956f9269dad_default" xlink:href="icui-20250331.xsd#icui_Srt_MultipleCurrencyAxisDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_Srt_MultipleCurrencyAxisAxis_3a95c517-eee2-4b2e-9ed8-c956f9269dad" xlink:to="loc_icui_Srt_MultipleCurrencyAxisDomain_3a95c517-eee2-4b2e-9ed8-c956f9269dad_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Srt_MultipleCurrencyAxisDomain_c0bebc6a-e4c8-4318-93e2-a0c8c2c782a7" xlink:href="icui-20250331.xsd#icui_Srt_MultipleCurrencyAxisDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_Srt_MultipleCurrencyAxisAxis_3a95c517-eee2-4b2e-9ed8-c956f9269dad" xlink:to="loc_icui_Srt_MultipleCurrencyAxisDomain_c0bebc6a-e4c8-4318-93e2-a0c8c2c782a7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherCurrenciesMember_1cb9cc59-edc3-4872-9e85-3e8f41856335" xlink:href="icui-20250331.xsd#icui_OtherCurrenciesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_Srt_MultipleCurrencyAxisDomain_c0bebc6a-e4c8-4318-93e2-a0c8c2c782a7" xlink:to="loc_icui_OtherCurrenciesMember_1cb9cc59-edc3-4872-9e85-3e8f41856335" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_e38b54d7-298a-4af6-8b36-73db83849127" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_54ddc638-5b73-4fa1-ba46-8c9747adc2d3" xlink:to="loc_us-gaap_DerivativeNotionalAmount_e38b54d7-298a-4af6-8b36-73db83849127" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsInterestRateSwapsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#DerivativeFinancialInstrumentsInterestRateSwapsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsInterestRateSwapsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_4abfcacf-a177-4b5d-bc26-9b32bf002a89" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:to="loc_us-gaap_DerivativeTable_4abfcacf-a177-4b5d-bc26-9b32bf002a89" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_3449035b-bc01-4ac5-b384-5db75708c4e9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_4abfcacf-a177-4b5d-bc26-9b32bf002a89" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_3449035b-bc01-4ac5-b384-5db75708c4e9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3449035b-bc01-4ac5-b384-5db75708c4e9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3449035b-bc01-4ac5-b384-5db75708c4e9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3449035b-bc01-4ac5-b384-5db75708c4e9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9b573278-06f7-40f3-bcbd-2048ed7ee749" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3449035b-bc01-4ac5-b384-5db75708c4e9" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9b573278-06f7-40f3-bcbd-2048ed7ee749" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_5bb6591c-5daf-4b19-a08a-5a4470bd0679" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9b573278-06f7-40f3-bcbd-2048ed7ee749" xlink:to="loc_us-gaap_InterestRateSwapMember_5bb6591c-5daf-4b19-a08a-5a4470bd0679" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_0d53b657-db56-499f-946a-d9e1e3355c15" xlink:href="icui-20250331.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_4abfcacf-a177-4b5d-bc26-9b32bf002a89" xlink:to="loc_icui_TermLoanAxis_0d53b657-db56-499f-946a-d9e1e3355c15" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_0d53b657-db56-499f-946a-d9e1e3355c15_default" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_0d53b657-db56-499f-946a-d9e1e3355c15" xlink:to="loc_icui_TermLoanDomain_0d53b657-db56-499f-946a-d9e1e3355c15_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_0d53b657-db56-499f-946a-d9e1e3355c15" xlink:to="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_eff20c81-dba8-46bf-a1b4-c9669511afe2" xlink:href="icui-20250331.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:to="loc_icui_TermLoanAMember_eff20c81-dba8-46bf-a1b4-c9669511afe2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_8dfdf24a-c76f-47dc-944b-d7898f37cd51" xlink:href="icui-20250331.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:to="loc_icui_TermLoanBMember_8dfdf24a-c76f-47dc-944b-d7898f37cd51" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Swap3TermLoanABMember_838db429-da5f-4f7b-88f1-ef99c2c1ab97" xlink:href="icui-20250331.xsd#icui_Swap3TermLoanABMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:to="loc_icui_Swap3TermLoanABMember_838db429-da5f-4f7b-88f1-ef99c2c1ab97" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Swap3Member_5fe02217-4f58-4946-b730-2f7d3603664d" xlink:href="icui-20250331.xsd#icui_Swap3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_84cebeed-d051-4844-a275-174103e83207" xlink:to="loc_icui_Swap3Member_5fe02217-4f58-4946-b730-2f7d3603664d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_32afd84d-1a3e-45d7-ad74-125983140d4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:to="loc_us-gaap_DerivativeNotionalAmount_32afd84d-1a3e-45d7-ad74-125983140d4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InterestRateSwapEndingNotionalValue_09403671-a09d-45ec-a8dc-16e3e7721e8d" xlink:href="icui-20250331.xsd#icui_InterestRateSwapEndingNotionalValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:to="loc_icui_InterestRateSwapEndingNotionalValue_09403671-a09d-45ec-a8dc-16e3e7721e8d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeFixedInterestRate_fcf91ac0-c756-41aa-a410-eb9efd6a6e36" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeFixedInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:to="loc_us-gaap_DerivativeFixedInterestRate_fcf91ac0-c756-41aa-a410-eb9efd6a6e36" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_DerivativeVariableRateFloor_86a7616d-9621-45c8-aaa3-2109820677de" xlink:href="icui-20250331.xsd#icui_DerivativeVariableRateFloor"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_9cd3d2c5-1dbd-4778-8bda-93a327956fc0" xlink:to="loc_icui_DerivativeVariableRateFloor_86a7616d-9621-45c8-aaa3-2109820677de" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesFVofDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativesFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_64940eb2-86f9-4616-9d18-d7b407e3127a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_64940eb2-86f9-4616-9d18-d7b407e3127a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_be6f470d-abfb-4f3f-867e-c23cd9ead429" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_64940eb2-86f9-4616-9d18-d7b407e3127a" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_be6f470d-abfb-4f3f-867e-c23cd9ead429" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_be6f470d-abfb-4f3f-867e-c23cd9ead429_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_be6f470d-abfb-4f3f-867e-c23cd9ead429" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_be6f470d-abfb-4f3f-867e-c23cd9ead429_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ee38529a-d01a-4501-8461-dfba8ce06ed5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_be6f470d-abfb-4f3f-867e-c23cd9ead429" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ee38529a-d01a-4501-8461-dfba8ce06ed5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_c195c850-16a8-4a61-b8ca-6df331dfddbc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_ee38529a-d01a-4501-8461-dfba8ce06ed5" xlink:to="loc_us-gaap_ForeignExchangeContractMember_c195c850-16a8-4a61-b8ca-6df331dfddbc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_1d429365-b4dc-4939-a6b1-9097b9fc54d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_ee38529a-d01a-4501-8461-dfba8ce06ed5" xlink:to="loc_us-gaap_InterestRateSwapMember_1d429365-b4dc-4939-a6b1-9097b9fc54d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration_f3175f24-3858-4443-b77a-fba71267c449" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration_f3175f24-3858-4443-b77a-fba71267c449" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsCurrent_d76bc598-d595-4809-ab9f-bd12fe33c96c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetsCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeAssetsCurrent_d76bc598-d595-4809-ab9f-bd12fe33c96c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration_4e73b44f-ce57-44c1-b75f-0204db807251" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration_4e73b44f-ce57-44c1-b75f-0204db807251" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_e554df38-4268-428a-a6bc-c256d7b42d2c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_e554df38-4268-428a-a6bc-c256d7b42d2c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_328d097d-accd-4a02-bdb0-4bb1237f9cc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeAssets_328d097d-accd-4a02-bdb0-4bb1237f9cc7" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration_ddb6afe1-fd4a-44fa-8acd-28c0fd0757de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration_ddb6afe1-fd4a-44fa-8acd-28c0fd0757de" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_b119068f-7ed2-4370-ac9f-fddb5c9db40a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_b119068f-7ed2-4370-ac9f-fddb5c9db40a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_bfbeb8db-6e30-4e3b-9c1e-03332052433a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_e56b1c3c-0442-4a71-891a-f2b580f2c67f" xlink:to="loc_us-gaap_DerivativeLiabilities_bfbeb8db-6e30-4e3b-9c1e-03332052433a" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesCashFlowHedgeActivityIncludedinAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_fbbf7f39-66cc-4168-b6ab-4cb0e460d279" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_46bf1004-1871-4338-a764-dafacad44c1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_fbbf7f39-66cc-4168-b6ab-4cb0e460d279" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_46bf1004-1871-4338-a764-dafacad44c1d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_615a3fd5-0a22-4b92-9399-9b467e176df7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_46bf1004-1871-4338-a764-dafacad44c1d" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_615a3fd5-0a22-4b92-9399-9b467e176df7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_615a3fd5-0a22-4b92-9399-9b467e176df7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_615a3fd5-0a22-4b92-9399-9b467e176df7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_615a3fd5-0a22-4b92-9399-9b467e176df7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_e9a8ba6e-9566-4442-bf01-b0c2f1cbb0c8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_615a3fd5-0a22-4b92-9399-9b467e176df7" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_e9a8ba6e-9566-4442-bf01-b0c2f1cbb0c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_35bac1b0-ce14-444c-89da-3a278f1885c3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e9a8ba6e-9566-4442-bf01-b0c2f1cbb0c8" xlink:to="loc_us-gaap_ForeignExchangeContractMember_35bac1b0-ce14-444c-89da-3a278f1885c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_5e2f89a7-9914-492e-98b5-fef679fac246" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_e9a8ba6e-9566-4442-bf01-b0c2f1cbb0c8" xlink:to="loc_us-gaap_InterestRateSwapMember_5e2f89a7-9914-492e-98b5-fef679fac246" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_52243b79-dca3-4a6b-b859-7e6dc69af84c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_fbbf7f39-66cc-4168-b6ab-4cb0e460d279" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeTax_52243b79-dca3-4a6b-b859-7e6dc69af84c" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsandHedgingActivitiesAmountsAffectingConsolidatedStatementsofIncomeDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_b4605b86-6365-4b5e-9424-0728ed398ef1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_b4605b86-6365-4b5e-9424-0728ed398ef1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_3f27d366-5da3-4bc7-9c23-8e7417640987" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_b4605b86-6365-4b5e-9424-0728ed398ef1" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_3f27d366-5da3-4bc7-9c23-8e7417640987" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_3f27d366-5da3-4bc7-9c23-8e7417640987_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3f27d366-5da3-4bc7-9c23-8e7417640987" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_3f27d366-5da3-4bc7-9c23-8e7417640987_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4ca70f0e-297c-42c4-b61f-3affac6a2247" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_3f27d366-5da3-4bc7-9c23-8e7417640987" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4ca70f0e-297c-42c4-b61f-3affac6a2247" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_587f6665-04a9-4d8d-9539-dc2e8f3fca5f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4ca70f0e-297c-42c4-b61f-3affac6a2247" xlink:to="loc_us-gaap_ForeignExchangeContractMember_587f6665-04a9-4d8d-9539-dc2e8f3fca5f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_1d2c29f4-b21c-4432-802c-e63c35f61f36" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_4ca70f0e-297c-42c4-b61f-3affac6a2247" xlink:to="loc_us-gaap_InterestRateSwapMember_1d2c29f4-b21c-4432-802c-e63c35f61f36" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_26ebcba1-5dce-45ef-be4e-978634436d06" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_b4605b86-6365-4b5e-9424-0728ed398ef1" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_26ebcba1-5dce-45ef-be4e-978634436d06" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_26ebcba1-5dce-45ef-be4e-978634436d06_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_26ebcba1-5dce-45ef-be4e-978634436d06" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_26ebcba1-5dce-45ef-be4e-978634436d06_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_d306e72d-7c61-4184-9200-75cb639ab2de" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_26ebcba1-5dce-45ef-be4e-978634436d06" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_d306e72d-7c61-4184-9200-75cb639ab2de" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradingRevenueMember_4e366d8c-6fc1-4744-b05d-e8e9010cc1df" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradingRevenueMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_d306e72d-7c61-4184-9200-75cb639ab2de" xlink:to="loc_us-gaap_TradingRevenueMember_4e366d8c-6fc1-4744-b05d-e8e9010cc1df" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CostOfSalesMember_cb68c24b-85c6-4e90-9aaf-dbd5603b5643" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CostOfSalesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_d306e72d-7c61-4184-9200-75cb639ab2de" xlink:to="loc_us-gaap_CostOfSalesMember_cb68c24b-85c6-4e90-9aaf-dbd5603b5643" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_247cf653-f5bd-45a6-a51f-4ae24baa7a31" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_b4605b86-6365-4b5e-9424-0728ed398ef1" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_247cf653-f5bd-45a6-a51f-4ae24baa7a31" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_247cf653-f5bd-45a6-a51f-4ae24baa7a31_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_247cf653-f5bd-45a6-a51f-4ae24baa7a31" xlink:to="loc_us-gaap_HedgingRelationshipDomain_247cf653-f5bd-45a6-a51f-4ae24baa7a31_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_HedgingRelationshipDomain_ddbb630f-5096-41d7-900a-0e6511147a09" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_HedgingRelationshipDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_247cf653-f5bd-45a6-a51f-4ae24baa7a31" xlink:to="loc_us-gaap_HedgingRelationshipDomain_ddbb630f-5096-41d7-900a-0e6511147a09" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CashFlowHedgingMember_3afd0792-b7fd-4ea6-a99c-e34056cf9455" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CashFlowHedgingMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_ddbb630f-5096-41d7-900a-0e6511147a09" xlink:to="loc_us-gaap_CashFlowHedgingMember_3afd0792-b7fd-4ea6-a99c-e34056cf9455" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentGainLossReclassifiedFromAociIntoIncomeEffectivePortionStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_113bee34-58a6-44c9-b680-fcd7ddf59302" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentGainLossReclassifiedFromAociIntoIncomeEffectivePortionStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_DerivativeInstrumentGainLossReclassifiedFromAociIntoIncomeEffectivePortionStatementOfIncomeOrComprehensiveIncomeExtensibleEnumeration_113bee34-58a6-44c9-b680-fcd7ddf59302" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet_fcda0fd5-8e61-4c86-937f-5d3c31e8a75c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortionNet_fcda0fd5-8e61-4c86-937f-5d3c31e8a75c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_540a325b-d94c-4b7c-ad62-e0e3e4bbf018" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_540a325b-d94c-4b7c-ad62-e0e3e4bbf018" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_275e634e-40ca-448e-be2b-ee511c15d7e5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_275e634e-40ca-448e-be2b-ee511c15d7e5" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_7d2dc42d-6390-4404-82ec-0a379f9e2605" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_295cbd86-069d-44b9-bc83-d23f3fc454c7" xlink:to="loc_us-gaap_InterestRateCashFlowHedgeGainLossToBeReclassifiedDuringNext12MonthsNet_7d2dc42d-6390-4404-82ec-0a379f9e2605" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#FairValueMeasuresandDisclosuresDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_82720c36-3997-4cea-a41a-6ab3a22f8a3b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_199aac79-493d-42ba-8df2-32080b76553a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_82720c36-3997-4cea-a41a-6ab3a22f8a3b" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_199aac79-493d-42ba-8df2-32080b76553a" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_f3c903c5-6b69-4158-934d-79c7be48e5d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_199aac79-493d-42ba-8df2-32080b76553a" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_f3c903c5-6b69-4158-934d-79c7be48e5d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f3c903c5-6b69-4158-934d-79c7be48e5d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f3c903c5-6b69-4158-934d-79c7be48e5d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_f3c903c5-6b69-4158-934d-79c7be48e5d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_15ca678f-413e-440e-aed5-8e4be833ddb9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_f3c903c5-6b69-4158-934d-79c7be48e5d7" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_15ca678f-413e-440e-aed5-8e4be833ddb9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_de098869-5a21-4316-b1d2-57eccbd04a0f" xlink:href="icui-20250331.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_15ca678f-413e-440e-aed5-8e4be833ddb9" xlink:to="loc_icui_SmithsMedicalMember_de098869-5a21-4316-b1d2-57eccbd04a0f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_2e8dc7d8-9877-401f-a579-e98d75dfff33" xlink:href="icui-20250331.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_15ca678f-413e-440e-aed5-8e4be833ddb9" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_2e8dc7d8-9877-401f-a579-e98d75dfff33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalDistributorMember_c3b33968-a5ed-4abd-bd41-c1b2ad9174a2" xlink:href="icui-20250331.xsd#icui_InternationalDistributorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_15ca678f-413e-440e-aed5-8e4be833ddb9" xlink:to="loc_icui_InternationalDistributorMember_c3b33968-a5ed-4abd-bd41-c1b2ad9174a2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationByTypeAxis_ddcf72c9-1b97-4565-81f7-cb9b9f919adf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationByTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_199aac79-493d-42ba-8df2-32080b76553a" xlink:to="loc_us-gaap_ContingentConsiderationByTypeAxis_ddcf72c9-1b97-4565-81f7-cb9b9f919adf" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_ddcf72c9-1b97-4565-81f7-cb9b9f919adf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_ddcf72c9-1b97-4565-81f7-cb9b9f919adf" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_ddcf72c9-1b97-4565-81f7-cb9b9f919adf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ContingentConsiderationTypeDomain_bc4a1043-598d-4431-8497-bf9ae51ba42b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ContingentConsiderationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ContingentConsiderationByTypeAxis_ddcf72c9-1b97-4565-81f7-cb9b9f919adf" xlink:to="loc_us-gaap_ContingentConsiderationTypeDomain_bc4a1043-598d-4431-8497-bf9ae51ba42b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilityMember_55729614-fee8-4661-a6ac-fe96d9922b73" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ContingentConsiderationTypeDomain_bc4a1043-598d-4431-8497-bf9ae51ba42b" xlink:to="loc_us-gaap_LiabilityMember_55729614-fee8-4661-a6ac-fe96d9922b73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_d1685174-2b44-465c-96e2-01d6dff2d289" xlink:href="icui-20250331.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_82720c36-3997-4cea-a41a-6ab3a22f8a3b" xlink:to="loc_icui_Contingentconsiderationgross_d1685174-2b44-465c-96e2-01d6dff2d289" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OwnershipRequirementForEarnoutPayment_1b7e3d90-c481-4efd-b3ac-269c026895d2" xlink:href="icui-20250331.xsd#icui_OwnershipRequirementForEarnoutPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_82720c36-3997-4cea-a41a-6ab3a22f8a3b" xlink:to="loc_icui_OwnershipRequirementForEarnoutPayment_1b7e3d90-c481-4efd-b3ac-269c026895d2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_a9ba5730-bc24-4ee1-8f5d-cd5f6ad8accc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_82720c36-3997-4cea-a41a-6ab3a22f8a3b" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_a9ba5730-bc24-4ee1-8f5d-cd5f6ad8accc" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationRollForwardDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationRollForwardDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilitiesRecurringBasisUnobservableInputReconciliationRollForwardDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1286722f-cad7-4393-8a14-c0852b581701" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1286722f-cad7-4393-8a14-c0852b581701" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_7fb9964f-9d1a-4073-972b-5a92d634c802" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_7fb9964f-9d1a-4073-972b-5a92d634c802" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb9964f-9d1a-4073-972b-5a92d634c802_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7fb9964f-9d1a-4073-972b-5a92d634c802" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_7fb9964f-9d1a-4073-972b-5a92d634c802_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d348371-81a7-4133-b305-ee62e453e437" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_7fb9964f-9d1a-4073-972b-5a92d634c802" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d348371-81a7-4133-b305-ee62e453e437" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_7fb19c91-0eb5-4fb8-8c96-368465295c4f" xlink:href="icui-20250331.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d348371-81a7-4133-b305-ee62e453e437" xlink:to="loc_icui_SmithsMedicalMember_7fb19c91-0eb5-4fb8-8c96-368465295c4f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_49e4f33c-a709-442d-9cff-029ccd45cf1f" xlink:href="icui-20250331.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d348371-81a7-4133-b305-ee62e453e437" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_49e4f33c-a709-442d-9cff-029ccd45cf1f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalDistributorMember_2ca9b9c3-6afe-426a-bede-7e717d00ea72" xlink:href="icui-20250331.xsd#icui_InternationalDistributorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5d348371-81a7-4133-b305-ee62e453e437" xlink:to="loc_icui_InternationalDistributorMember_2ca9b9c3-6afe-426a-bede-7e717d00ea72" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_a9666767-a8ae-4bea-b7d3-8928be0894f2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_a9666767-a8ae-4bea-b7d3-8928be0894f2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_a9666767-a8ae-4bea-b7d3-8928be0894f2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_a9666767-a8ae-4bea-b7d3-8928be0894f2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_a9666767-a8ae-4bea-b7d3-8928be0894f2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_e75330bb-d484-4088-86c0-64d3a67f5a8b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_a9666767-a8ae-4bea-b7d3-8928be0894f2" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_e75330bb-d484-4088-86c0-64d3a67f5a8b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_9abc7cc4-714f-4179-a784-9a1a1966d94c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_2bb2e7f0-4c5e-4c82-806e-a8acc0d53d71" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_9abc7cc4-714f-4179-a784-9a1a1966d94c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_a843be08-6ab9-4bc4-94dd-4b9943ac571c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationTable_a32e68aa-002a-48fe-ae5e-87d982d6524e" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_a843be08-6ab9-4bc4-94dd-4b9943ac571c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_a843be08-6ab9-4bc4-94dd-4b9943ac571c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_a843be08-6ab9-4bc4-94dd-4b9943ac571c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_a843be08-6ab9-4bc4-94dd-4b9943ac571c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_eafb50b0-65e9-4d74-9ea0-13c29171a3fe" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_a843be08-6ab9-4bc4-94dd-4b9943ac571c" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_eafb50b0-65e9-4d74-9ea0-13c29171a3fe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_6120abc9-888a-412f-afba-152f8e0c451f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationLineItems_1286722f-cad7-4393-8a14-c0852b581701" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_6120abc9-888a-412f-afba-152f8e0c451f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresLiabilityMeasurementInputsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_babbd0d5-334d-4983-81d7-890016af2b72" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_14da825e-6417-48d9-9235-0611419a2c20" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_babbd0d5-334d-4983-81d7-890016af2b72" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_14da825e-6417-48d9-9235-0611419a2c20" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_fcd34742-ad1b-46b3-bcb5-3b005bbffabc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_14da825e-6417-48d9-9235-0611419a2c20" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_fcd34742-ad1b-46b3-bcb5-3b005bbffabc" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fcd34742-ad1b-46b3-bcb5-3b005bbffabc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_fcd34742-ad1b-46b3-bcb5-3b005bbffabc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_fcd34742-ad1b-46b3-bcb5-3b005bbffabc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a921bc9c-5966-4f04-bfcb-2054eec45448" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_fcd34742-ad1b-46b3-bcb5-3b005bbffabc" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a921bc9c-5966-4f04-bfcb-2054eec45448" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_c5eb19d4-c3a9-406f-b1d4-44c7db8716ef" xlink:href="icui-20250331.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_a921bc9c-5966-4f04-bfcb-2054eec45448" xlink:to="loc_icui_SmithsMedicalMember_c5eb19d4-c3a9-406f-b1d4-44c7db8716ef" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasuresandDisclosuresAssetsandLiabilitiesbyBalanceSheetGroupingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByBalanceSheetGroupingTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eff6527a-6118-42e1-8075-1ce0f097b9f8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eff6527a-6118-42e1-8075-1ce0f097b9f8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_eff6527a-6118-42e1-8075-1ce0f097b9f8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eff6527a-6118-42e1-8075-1ce0f097b9f8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_eff6527a-6118-42e1-8075-1ce0f097b9f8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a8d41ef5-8b1f-4549-82df-fd7ab0cf1a46" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_eff6527a-6118-42e1-8075-1ce0f097b9f8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a8d41ef5-8b1f-4549-82df-fd7ab0cf1a46" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_4bff5fae-d25d-4750-9422-fa21696ba0c3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a8d41ef5-8b1f-4549-82df-fd7ab0cf1a46" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_4bff5fae-d25d-4750-9422-fa21696ba0c3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_843fd886-39c6-4e57-9f71-940e7c079f9a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a8d41ef5-8b1f-4549-82df-fd7ab0cf1a46" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_843fd886-39c6-4e57-9f71-940e7c079f9a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_668df3d9-71aa-4ca4-8c3e-87826ab561a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_a8d41ef5-8b1f-4549-82df-fd7ab0cf1a46" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_668df3d9-71aa-4ca4-8c3e-87826ab561a5" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_43254606-418d-454b-9aa3-b429a0ef5029" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_43254606-418d-454b-9aa3-b429a0ef5029" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_43254606-418d-454b-9aa3-b429a0ef5029_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_43254606-418d-454b-9aa3-b429a0ef5029" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_43254606-418d-454b-9aa3-b429a0ef5029_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_096914af-4a7b-4814-9c96-eca8a544b353" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_43254606-418d-454b-9aa3-b429a0ef5029" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_096914af-4a7b-4814-9c96-eca8a544b353" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_b6fdce7f-5eec-4cf6-8134-d9b7903ddf41" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_096914af-4a7b-4814-9c96-eca8a544b353" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_b6fdce7f-5eec-4cf6-8134-d9b7903ddf41" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_28924107-f7d2-489b-8094-29273437bbef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByLiabilityClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_28924107-f7d2-489b-8094-29273437bbef" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_28924107-f7d2-489b-8094-29273437bbef_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_28924107-f7d2-489b-8094-29273437bbef" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_28924107-f7d2-489b-8094-29273437bbef_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_9d4fa792-9165-4195-be38-dc3ac21ceaf6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_28924107-f7d2-489b-8094-29273437bbef" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_9d4fa792-9165-4195-be38-dc3ac21ceaf6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesTotalMember_a016c950-f6a6-4a53-8166-02b98b4e76bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesTotalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_9d4fa792-9165-4195-be38-dc3ac21ceaf6" xlink:to="loc_us-gaap_LiabilitiesTotalMember_a016c950-f6a6-4a53-8166-02b98b4e76bd" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeAxis_2860f4bb-3584-457f-9eda-283222ff92a0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_us-gaap_InvestmentTypeAxis_2860f4bb-3584-457f-9eda-283222ff92a0" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_2860f4bb-3584-457f-9eda-283222ff92a0_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_2860f4bb-3584-457f-9eda-283222ff92a0" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_2860f4bb-3584-457f-9eda-283222ff92a0_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_9e00bdfe-e01a-4476-af59-cbc78c8149f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InvestmentTypeCategorizationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_2860f4bb-3584-457f-9eda-283222ff92a0" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_9e00bdfe-e01a-4476-af59-cbc78c8149f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialInstrumentAxis_64404451-7f22-4a17-8363-0264ecb8b840" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_us-gaap_FinancialInstrumentAxis_64404451-7f22-4a17-8363-0264ecb8b840" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_64404451-7f22-4a17-8363-0264ecb8b840_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FinancialInstrumentAxis_64404451-7f22-4a17-8363-0264ecb8b840" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_64404451-7f22-4a17-8363-0264ecb8b840_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6517778f-3b62-4533-90fc-01dd52dae1e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FinancialInstrumentAxis_64404451-7f22-4a17-8363-0264ecb8b840" xlink:to="loc_us-gaap_TransfersAndServicingOfFinancialInstrumentsTypesOfFinancialInstrumentsDomain_6517778f-3b62-4533-90fc-01dd52dae1e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ClassificationAxis_33c18662-4963-42f3-893a-66201510ba5a" xlink:href="icui-20250331.xsd#icui_ClassificationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_1a0b338b-1abf-48fe-ac28-75c52a735b1c" xlink:to="loc_icui_ClassificationAxis_33c18662-4963-42f3-893a-66201510ba5a" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ClassificationDomain_33c18662-4963-42f3-893a-66201510ba5a_default" xlink:href="icui-20250331.xsd#icui_ClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_ClassificationAxis_33c18662-4963-42f3-893a-66201510ba5a" xlink:to="loc_icui_ClassificationDomain_33c18662-4963-42f3-893a-66201510ba5a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ClassificationDomain_1dcf1394-a3fe-48df-aec2-795254bfa31d" xlink:href="icui-20250331.xsd#icui_ClassificationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_ClassificationAxis_33c18662-4963-42f3-893a-66201510ba5a" xlink:to="loc_icui_ClassificationDomain_1dcf1394-a3fe-48df-aec2-795254bfa31d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_CurrentMember_7d6486ab-d436-47f0-b2c1-d079a030e00e" xlink:href="icui-20250331.xsd#icui_CurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ClassificationDomain_1dcf1394-a3fe-48df-aec2-795254bfa31d" xlink:to="loc_icui_CurrentMember_7d6486ab-d436-47f0-b2c1-d079a030e00e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NoncurrentMember_f314b39f-2e54-41e6-9fcb-a83beffd9fbe" xlink:href="icui-20250331.xsd#icui_NoncurrentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ClassificationDomain_1dcf1394-a3fe-48df-aec2-795254bfa31d" xlink:to="loc_icui_NoncurrentMember_f314b39f-2e54-41e6-9fcb-a83beffd9fbe" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_509b55e8-7097-448d-9323-a5b879107713" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_509b55e8-7097-448d-9323-a5b879107713" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9b39f836-5e35-4af1-acaf-9c9a689df399" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9b39f836-5e35-4af1-acaf-9c9a689df399" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_2ced30c9-ab1b-4c97-9604-0d3a09b53559" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_2ced30c9-ab1b-4c97-9604-0d3a09b53559" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_b1ce13f7-3604-4ab9-ab9f-5b1fb813be74" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NonfinancialLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_b1ce13f7-3604-4ab9-ab9f-5b1fb813be74" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_6e0b4d59-7003-402f-b6b2-2c74ca03b245" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_6e0b4d59-7003-402f-b6b2-2c74ca03b245" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_b16806a2-2eba-44f9-98b8-9072917ed5b3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FinancialLiabilitiesFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_FinancialLiabilitiesFairValueDisclosure_b16806a2-2eba-44f9-98b8-9072917ed5b3" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration_0be093b1-3627-4d39-a8fa-98410cea6392" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_DerivativeAssetCurrentStatementOfFinancialPositionExtensibleEnumeration_0be093b1-3627-4d39-a8fa-98410cea6392" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration_7c23a3b5-8353-4c8c-9383-39258c4c4ffd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_DerivativeAssetNoncurrentStatementOfFinancialPositionExtensibleEnumeration_7c23a3b5-8353-4c8c-9383-39258c4c4ffd" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration_132d434b-cb6c-4df4-b7e8-83e3ee35367e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueBalanceSheetGroupingFinancialStatementCaptionsLineItems_03599fbe-a0d8-4be9-9dd8-00c463866aaa" xlink:to="loc_us-gaap_DerivativeLiabilityCurrentStatementOfFinancialPositionExtensibleEnumeration_132d434b-cb6c-4df4-b7e8-83e3ee35367e" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/EquityMethodInvestmentsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#EquityMethodInvestmentsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/EquityMethodInvestmentsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems_29dae772-b957-4bec-850b-8807aa09adb2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable_b255a325-56ef-4d15-8be2-99afa14ee17f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems_29dae772-b957-4bec-850b-8807aa09adb2" xlink:to="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable_b255a325-56ef-4d15-8be2-99afa14ee17f" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_d98da1ab-f196-4125-83ef-9012bef8583e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable_b255a325-56ef-4d15-8be2-99afa14ee17f" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_d98da1ab-f196-4125-83ef-9012bef8583e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_d98da1ab-f196-4125-83ef-9012bef8583e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_d98da1ab-f196-4125-83ef-9012bef8583e" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_d98da1ab-f196-4125-83ef-9012bef8583e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_49eba062-bdb9-498c-a674-d3c6ffa4cf76" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_d98da1ab-f196-4125-83ef-9012bef8583e" xlink:to="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_49eba062-bdb9-498c-a674-d3c6ffa4cf76" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NonPublicCompanyMember_db6bbf45-21c9-444b-98cf-cf1beeba59e0" xlink:href="icui-20250331.xsd#icui_NonPublicCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_49eba062-bdb9-498c-a674-d3c6ffa4cf76" xlink:to="loc_icui_NonPublicCompanyMember_db6bbf45-21c9-444b-98cf-cf1beeba59e0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1d3821e3-95ff-46ef-bf92-f44cc32f9226" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueTable_b255a325-56ef-4d15-8be2-99afa14ee17f" xlink:to="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1d3821e3-95ff-46ef-bf92-f44cc32f9226" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_1d3821e3-95ff-46ef-bf92-f44cc32f9226_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1d3821e3-95ff-46ef-bf92-f44cc32f9226" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_1d3821e3-95ff-46ef-bf92-f44cc32f9226_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EquityMethodInvesteeNameDomain_b501e1bd-6aa9-4a63-88f6-66c71861e210" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EquityMethodInvesteeNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_1d3821e3-95ff-46ef-bf92-f44cc32f9226" xlink:to="loc_srt_EquityMethodInvesteeNameDomain_b501e1bd-6aa9-4a63-88f6-66c71861e210" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_NonPublicCompanyMember_7c739ed5-da98-40ed-8e35-3fb8eea972e7" xlink:href="icui-20250331.xsd#icui_NonPublicCompanyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_EquityMethodInvesteeNameDomain_b501e1bd-6aa9-4a63-88f6-66c71861e210" xlink:to="loc_icui_NonPublicCompanyMember_7c739ed5-da98-40ed-8e35-3fb8eea972e7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_890ab6b8-369b-4b25-a1ee-0dba37a38ce5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentOwnershipPercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems_29dae772-b957-4bec-850b-8807aa09adb2" xlink:to="loc_us-gaap_EquityMethodInvestmentOwnershipPercentage_890ab6b8-369b-4b25-a1ee-0dba37a38ce5" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestmentAggregateCost_bf7ed3e3-b72f-459d-b31a-842033733ea8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestmentAggregateCost"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems_29dae772-b957-4bec-850b-8807aa09adb2" xlink:to="loc_us-gaap_EquityMethodInvestmentAggregateCost_bf7ed3e3-b72f-459d-b31a-842033733ea8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityMethodInvestments_25620fad-b35a-4e70-b967-4a0442849518" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityMethodInvestments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueLineItems_29dae772-b957-4bec-850b-8807aa09adb2" xlink:to="loc_us-gaap_EquityMethodInvestments_25620fad-b35a-4e70-b967-4a0442849518" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsandOtherCurrentAssetsPrepaidsandOtherAssetsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#PrepaidsandOtherCurrentAssetsPrepaidsandOtherAssetsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsandOtherCurrentAssetsPrepaidsandOtherAssetsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_885b6c65-de01-4562-81be-b747a2136017" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_da613cb5-402c-4a6d-89d3-b9f481965d1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_885b6c65-de01-4562-81be-b747a2136017" xlink:to="loc_us-gaap_DerivativeTable_da613cb5-402c-4a6d-89d3-b9f481965d1e" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_89dcea3c-49f3-4f3b-96eb-1a4128e5b996" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_da613cb5-402c-4a6d-89d3-b9f481965d1e" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_89dcea3c-49f3-4f3b-96eb-1a4128e5b996" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_89dcea3c-49f3-4f3b-96eb-1a4128e5b996_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_89dcea3c-49f3-4f3b-96eb-1a4128e5b996" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_89dcea3c-49f3-4f3b-96eb-1a4128e5b996_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_c715c471-dc39-4b03-b6ed-c81e929c79a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BalanceSheetLocationDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_89dcea3c-49f3-4f3b-96eb-1a4128e5b996" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_c715c471-dc39-4b03-b6ed-c81e929c79a5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_302242ba-1780-47c8-8140-034977b9b31b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_c715c471-dc39-4b03-b6ed-c81e929c79a5" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_302242ba-1780-47c8-8140-034977b9b31b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_a2439a11-e62e-41a0-bae9-50e2023e39a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_885b6c65-de01-4562-81be-b747a2136017" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_a2439a11-e62e-41a0-bae9-50e2023e39a7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9ba6fb8a-8fda-4923-bbdb-d939b7fec1f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateDerivativeAssetsAtFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_885b6c65-de01-4562-81be-b747a2136017" xlink:to="loc_us-gaap_InterestRateDerivativeAssetsAtFairValue_9ba6fb8a-8fda-4923-bbdb-d939b7fec1f9" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/OtherAssetsNoncurrentDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#OtherAssetsNoncurrentDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/OtherAssetsNoncurrentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_a860981b-34b9-4a40-a0a9-fbcd9679cb0c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_031ec1c0-3c95-4eeb-97b3-f14c3702a796" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_a860981b-34b9-4a40-a0a9-fbcd9679cb0c" xlink:to="loc_us-gaap_DerivativeTable_031ec1c0-3c95-4eeb-97b3-f14c3702a796" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_79855db3-acaf-4a18-9cc5-085209a2625a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_031ec1c0-3c95-4eeb-97b3-f14c3702a796" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_79855db3-acaf-4a18-9cc5-085209a2625a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_79855db3-acaf-4a18-9cc5-085209a2625a_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_79855db3-acaf-4a18-9cc5-085209a2625a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_79855db3-acaf-4a18-9cc5-085209a2625a_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_9c9c8486-da6c-4bd0-9dd0-3f1b3bc31a67" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_79855db3-acaf-4a18-9cc5-085209a2625a" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_9c9c8486-da6c-4bd0-9dd0-3f1b3bc31a67" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_f5f6e56f-46af-4bc4-b909-cde323d8a870" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_9c9c8486-da6c-4bd0-9dd0-3f1b3bc31a67" xlink:to="loc_us-gaap_InterestRateSwapMember_f5f6e56f-46af-4bc4-b909-cde323d8a870" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsNoncurrent_f83a11e1-f5af-4ea4-96fb-ff9b85b7a04a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetsNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_a860981b-34b9-4a40-a0a9-fbcd9679cb0c" xlink:to="loc_us-gaap_DerivativeAssetsNoncurrent_f83a11e1-f5af-4ea4-96fb-ff9b85b7a04a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillandIntangibleAssetsIntangiblesTableDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#GoodwillandIntangibleAssetsIntangiblesTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillandIntangibleAssetsIntangiblesTableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_13ad6bec-73ac-43d0-bdec-b04c95874f66" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_13ad6bec-73ac-43d0-bdec-b04c95874f66" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b7b3b6bf-df69-4afe-8607-c1b30a6aed01" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_13ad6bec-73ac-43d0-bdec-b04c95874f66" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b7b3b6bf-df69-4afe-8607-c1b30a6aed01" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b7b3b6bf-df69-4afe-8607-c1b30a6aed01_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b7b3b6bf-df69-4afe-8607-c1b30a6aed01" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_b7b3b6bf-df69-4afe-8607-c1b30a6aed01_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_b7b3b6bf-df69-4afe-8607-c1b30a6aed01" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentsMember_54414cdd-d622-4d6c-b234-b9ac3cffec6c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PatentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_PatentsMember_54414cdd-d622-4d6c-b234-b9ac3cffec6c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerContractsMember_502a6efc-d723-473a-a601-f356863bf4f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerContractsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_CustomerContractsMember_502a6efc-d723-473a-a601-f356863bf4f3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_e03a8de3-da80-4b57-9e7d-e19abff2ce1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_e03a8de3-da80-4b57-9e7d-e19abff2ce1d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TrademarksMember_fec6e359-e7a2-4312-a05f-7e16c6386b80" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TrademarksMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_TrademarksMember_fec6e359-e7a2-4312-a05f-7e16c6386b80" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_42d7218b-3740-4d2e-811d-aed790c71326" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_TradeNamesMember_42d7218b-3740-4d2e-811d-aed790c71326" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_d7923e0e-9bad-4843-85ab-8911d496f00b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DevelopedTechnologyRightsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_d7923e0e-9bad-4843-85ab-8911d496f00b" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_7a54f19e-9d5e-4d98-a170-072bc23ef583" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NoncompeteAgreementsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_d6ff5c50-11a7-4b54-8008-6edbc5b86cfb" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_7a54f19e-9d5e-4d98-a170-072bc23ef583" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_1a146cbc-f84c-4f55-90ee-0ca3e6003c37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_1a146cbc-f84c-4f55-90ee-0ca3e6003c37" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_852d17dc-2ccc-413b-8888-ce9c7636176f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_852d17dc-2ccc-413b-8888-ce9c7636176f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_30c82820-f4de-4f63-b2c1-01505bae773f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_30c82820-f4de-4f63-b2c1-01505bae773f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c99c5851-c661-4f3a-b264-8b71ebaad99a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c99c5851-c661-4f3a-b264-8b71ebaad99a" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_f6085f29-485e-459e-9c33-be6466f715d2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_f6085f29-485e-459e-9c33-be6466f715d2" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_ad583201-0949-4fa4-af16-75073386bbef" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_ad583201-0949-4fa4-af16-75073386bbef" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_a1d5fbd3-f9eb-499f-9f10-53620d18204d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_a1d5fbd3-f9eb-499f-9f10-53620d18204d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_IndefinteLivedIntangiblesPutInUse_5882c936-1ffa-490e-9fa6-d516f7d5a9e0" xlink:href="icui-20250331.xsd#icui_IndefinteLivedIntangiblesPutInUse"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_146bfd59-504d-4efa-be34-7dc8a6c23ae4" xlink:to="loc_icui_IndefinteLivedIntangiblesPutInUse_5882c936-1ffa-490e-9fa6-d516f7d5a9e0" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#AccruedLiabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_ca6f4bfc-f2b8-4af9-b39d-75d98755b2f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_05630867-ff15-4ffc-9421-1ffa05948989" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_ca6f4bfc-f2b8-4af9-b39d-75d98755b2f0" xlink:to="loc_us-gaap_DerivativeTable_05630867-ff15-4ffc-9421-1ffa05948989" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_194e2c30-03bf-4b80-860c-438829e2b326" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_05630867-ff15-4ffc-9421-1ffa05948989" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_194e2c30-03bf-4b80-860c-438829e2b326" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_194e2c30-03bf-4b80-860c-438829e2b326_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_194e2c30-03bf-4b80-860c-438829e2b326" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_194e2c30-03bf-4b80-860c-438829e2b326_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_ecf734b2-5448-4009-ac0d-dd5aa114b213" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_194e2c30-03bf-4b80-860c-438829e2b326" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_ecf734b2-5448-4009-ac0d-dd5aa114b213" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeMember_c013811c-cef9-4c28-851c-c8528c772a85" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_ecf734b2-5448-4009-ac0d-dd5aa114b213" xlink:to="loc_us-gaap_ForeignExchangeMember_c013811c-cef9-4c28-851c-c8528c772a85" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilitiesCurrent_6592a681-a3df-493f-8a3a-37a5723ae4f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_ca6f4bfc-f2b8-4af9-b39d-75d98755b2f0" xlink:to="loc_us-gaap_DerivativeLiabilitiesCurrent_6592a681-a3df-493f-8a3a-37a5723ae4f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyLineItems_b00e7772-f9bb-4a60-a1e5-5a8c484264c1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyTable_7fc37f8c-1ecf-4ec8-bf9f-8a05705020a1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_b00e7772-f9bb-4a60-a1e5-5a8c484264c1" xlink:to="loc_us-gaap_ProductLiabilityContingencyTable_7fc37f8c-1ecf-4ec8-bf9f-8a05705020a1" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_ccd0cc31-6b9c-44a0-aef7-c869173133c3" xlink:href="icui-20250331.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ProductLiabilityContingencyTable_7fc37f8c-1ecf-4ec8-bf9f-8a05705020a1" xlink:to="loc_icui_TimingAxis_ccd0cc31-6b9c-44a0-aef7-c869173133c3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_ccd0cc31-6b9c-44a0-aef7-c869173133c3_default" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_ccd0cc31-6b9c-44a0-aef7-c869173133c3" xlink:to="loc_icui_TimingDomain_ccd0cc31-6b9c-44a0-aef7-c869173133c3_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_2543daaa-1172-40cb-942e-df0da62b5375" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_ccd0cc31-6b9c-44a0-aef7-c869173133c3" xlink:to="loc_icui_TimingDomain_2543daaa-1172-40cb-942e-df0da62b5375" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ShortTermMember_f54eeac4-68ca-4104-a5d4-62551b7b2ef0" xlink:href="icui-20250331.xsd#icui_ShortTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_2543daaa-1172-40cb-942e-df0da62b5375" xlink:to="loc_icui_ShortTermMember_f54eeac4-68ca-4104-a5d4-62551b7b2ef0" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_cb4c1a2b-cb06-431c-9b16-a83aec189981" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_b00e7772-f9bb-4a60-a1e5-5a8c484264c1" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_cb4c1a2b-cb06-431c-9b16-a83aec189981" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesLongtermliabilitiesDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#AccruedLiabilitiesLongtermliabilitiesDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesLongtermliabilitiesDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyLineItems_e91c530c-ea3f-4ad8-a8e4-13eae17b8f3c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityContingencyLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityContingencyTable_161c13ec-e4d0-49ef-845e-fb1ebcbf6304" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityContingencyTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_e91c530c-ea3f-4ad8-a8e4-13eae17b8f3c" xlink:to="loc_us-gaap_ProductLiabilityContingencyTable_161c13ec-e4d0-49ef-845e-fb1ebcbf6304" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingAxis_0e7ea507-d869-4583-9018-d618d8fe4d45" xlink:href="icui-20250331.xsd#icui_TimingAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ProductLiabilityContingencyTable_161c13ec-e4d0-49ef-845e-fb1ebcbf6304" xlink:to="loc_icui_TimingAxis_0e7ea507-d869-4583-9018-d618d8fe4d45" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_0e7ea507-d869-4583-9018-d618d8fe4d45_default" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TimingAxis_0e7ea507-d869-4583-9018-d618d8fe4d45" xlink:to="loc_icui_TimingDomain_0e7ea507-d869-4583-9018-d618d8fe4d45_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TimingDomain_53df6d0b-14b7-46b6-9d13-f15ffd3b33e0" xlink:href="icui-20250331.xsd#icui_TimingDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TimingAxis_0e7ea507-d869-4583-9018-d618d8fe4d45" xlink:to="loc_icui_TimingDomain_53df6d0b-14b7-46b6-9d13-f15ffd3b33e0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LongTermMember_b79b98bc-5a5c-49a5-b24d-097c1dd9afaa" xlink:href="icui-20250331.xsd#icui_LongTermMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TimingDomain_53df6d0b-14b7-46b6-9d13-f15ffd3b33e0" xlink:to="loc_icui_LongTermMember_b79b98bc-5a5c-49a5-b24d-097c1dd9afaa" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_12c10373-326e-417e-922b-1f3b49b21146" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ProductLiabilityContingencyLineItems_e91c530c-ea3f-4ad8-a8e4-13eae17b8f3c" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_12c10373-326e-417e-922b-1f3b49b21146" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxesEffectivetaxrateDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#IncomeTaxesEffectivetaxrateDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxesEffectivetaxrateDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_541ac443-99cc-439f-8c59-1f11485d5d26" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_fd007b3c-c85b-4e63-927a-ac2a646b3c41" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_541ac443-99cc-439f-8c59-1f11485d5d26" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_fd007b3c-c85b-4e63-927a-ac2a646b3c41" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_6d0978b7-3867-44fa-aecb-825ed599387e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_fd007b3c-c85b-4e63-927a-ac2a646b3c41" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_6d0978b7-3867-44fa-aecb-825ed599387e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6d0978b7-3867-44fa-aecb-825ed599387e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6d0978b7-3867-44fa-aecb-825ed599387e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_6d0978b7-3867-44fa-aecb-825ed599387e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ee1efa1f-ef45-4a6e-8fc3-1c9b03584f52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_6d0978b7-3867-44fa-aecb-825ed599387e" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ee1efa1f-ef45-4a6e-8fc3-1c9b03584f52" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_cbef2ca3-d218-495b-aee0-052b49474d73" xlink:href="icui-20250331.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_ee1efa1f-ef45-4a6e-8fc3-1c9b03584f52" xlink:to="loc_icui_SmithsMedicalMember_cbef2ca3-d218-495b-aee0-052b49474d73" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_602780c1-71c4-4caf-b31a-e22ee2065e43" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_541ac443-99cc-439f-8c59-1f11485d5d26" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_602780c1-71c4-4caf-b31a-e22ee2065e43" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#LongTermObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_c1b23e64-4a48-4435-b591-dbdbe4c169a3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_DebtInstrumentTable_c1b23e64-4a48-4435-b591-dbdbe4c169a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_1d520ce6-d75b-45f5-8c14-b315a65f478b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1b23e64-4a48-4435-b591-dbdbe4c169a3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_1d520ce6-d75b-45f5-8c14-b315a65f478b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_1d520ce6-d75b-45f5-8c14-b315a65f478b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1d520ce6-d75b-45f5-8c14-b315a65f478b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_1d520ce6-d75b-45f5-8c14-b315a65f478b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_394ec90f-674b-421a-bc3a-dbc8a46234b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_1d520ce6-d75b-45f5-8c14-b315a65f478b" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_394ec90f-674b-421a-bc3a-dbc8a46234b2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_68388147-e43b-4c0a-bd17-aa7513cb416a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_394ec90f-674b-421a-bc3a-dbc8a46234b2" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_68388147-e43b-4c0a-bd17-aa7513cb416a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_0a7267be-28db-4577-8c9e-a596d799b1b2" xlink:href="icui-20250331.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_c1b23e64-4a48-4435-b591-dbdbe4c169a3" xlink:to="loc_icui_TermLoanAxis_0a7267be-28db-4577-8c9e-a596d799b1b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_0a7267be-28db-4577-8c9e-a596d799b1b2_default" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_0a7267be-28db-4577-8c9e-a596d799b1b2" xlink:to="loc_icui_TermLoanDomain_0a7267be-28db-4577-8c9e-a596d799b1b2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_affcd3ed-8c95-40f6-b1cc-dd7b3596b085" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_0a7267be-28db-4577-8c9e-a596d799b1b2" xlink:to="loc_icui_TermLoanDomain_affcd3ed-8c95-40f6-b1cc-dd7b3596b085" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_39a2099c-f3e9-4250-a8b9-6ce5f6edd20d" xlink:href="icui-20250331.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_affcd3ed-8c95-40f6-b1cc-dd7b3596b085" xlink:to="loc_icui_TermLoanAMember_39a2099c-f3e9-4250-a8b9-6ce5f6edd20d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_38186327-804c-40bc-9965-6860faa84efa" xlink:href="icui-20250331.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_affcd3ed-8c95-40f6-b1cc-dd7b3596b085" xlink:to="loc_icui_TermLoanBMember_38186327-804c-40bc-9965-6860faa84efa" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TotalSeniorSecuredCreditFacility_a4267d79-070b-42fa-8300-f5f0047b01cf" xlink:href="icui-20250331.xsd#icui_TotalSeniorSecuredCreditFacility"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_icui_TotalSeniorSecuredCreditFacility_a4267d79-070b-42fa-8300-f5f0047b01cf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromIssuanceOfDebt_8fcdc825-ef40-4da0-8037-a14ece0d7915" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromIssuanceOfDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_ProceedsFromIssuanceOfDebt_8fcdc825-ef40-4da0-8037-a14ece0d7915" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_29983428-e270-4d14-bcb9-14612ffbb0b2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_29983428-e270-4d14-bcb9-14612ffbb0b2" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_RevolverSubLimits_869b0f0c-3d7d-4bf3-bc4f-8250b4f12f38" xlink:href="icui-20250331.xsd#icui_RevolverSubLimits"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_icui_RevolverSubLimits_869b0f0c-3d7d-4bf3-bc4f-8250b4f12f38" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DeferredFinanceCostsGross_f4492f93-6042-4d5f-9cac-f824a7294e63" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DeferredFinanceCostsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_DeferredFinanceCostsGross_f4492f93-6042-4d5f-9cac-f824a7294e63" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_c11f80ba-4770-462a-9c72-3c9341a3aee4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_LongTermDebt_c11f80ba-4770-462a-9c72-3c9341a3aee4" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentMaturityDate_75328759-065f-467f-bcc1-0991ba4aab2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentMaturityDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_us-gaap_DebtInstrumentMaturityDate_75328759-065f-467f-bcc1-0991ba4aab2f" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioCalculationCeilingSubtractedAmount_4f388719-a45b-424f-97d9-607db87b1d2b" xlink:href="icui-20250331.xsd#icui_LeverageRatioCalculationCeilingSubtractedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_45a1b090-10dc-4fbb-a8d6-34cc46e7b1ec" xlink:to="loc_icui_LeverageRatioCalculationCeilingSubtractedAmount_4f388719-a45b-424f-97d9-607db87b1d2b" xlink:type="arc" order="7"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsInterestRateTermsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#LongTermObligationsInterestRateTermsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsInterestRateTermsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:href="icui-20250331.xsd#icui_ApplicableMarginBasedOnLeverageRatioLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_b706d8b3-971e-4125-8f5e-9165ee6847e0" xlink:href="icui-20250331.xsd#icui_ApplicableMarginBasedOnLeverageRatioTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:to="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_b706d8b3-971e-4125-8f5e-9165ee6847e0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_5998f40b-9dc9-40d1-a067-393b7afe4855" xlink:href="icui-20250331.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_b706d8b3-971e-4125-8f5e-9165ee6847e0" xlink:to="loc_icui_TermLoanAxis_5998f40b-9dc9-40d1-a067-393b7afe4855" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_5998f40b-9dc9-40d1-a067-393b7afe4855_default" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_5998f40b-9dc9-40d1-a067-393b7afe4855" xlink:to="loc_icui_TermLoanDomain_5998f40b-9dc9-40d1-a067-393b7afe4855_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_73fcb2a2-7c78-4070-ae87-94138cdbe245" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_5998f40b-9dc9-40d1-a067-393b7afe4855" xlink:to="loc_icui_TermLoanDomain_73fcb2a2-7c78-4070-ae87-94138cdbe245" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_00393a6e-a3d1-45f8-a51f-d7e528bc84fb" xlink:href="icui-20250331.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_73fcb2a2-7c78-4070-ae87-94138cdbe245" xlink:to="loc_icui_TermLoanAMember_00393a6e-a3d1-45f8-a51f-d7e528bc84fb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_8d847131-d468-4bed-9948-60d4f36017d8" xlink:href="icui-20250331.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_73fcb2a2-7c78-4070-ae87-94138cdbe245" xlink:to="loc_icui_TermLoanBMember_8d847131-d468-4bed-9948-60d4f36017d8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelAxis_0e57a4c2-23bf-4e37-83b4-eb0767846d98" xlink:href="icui-20250331.xsd#icui_LeverageRatioLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_b706d8b3-971e-4125-8f5e-9165ee6847e0" xlink:to="loc_icui_LeverageRatioLevelAxis_0e57a4c2-23bf-4e37-83b4-eb0767846d98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelDomain_0e57a4c2-23bf-4e37-83b4-eb0767846d98_default" xlink:href="icui-20250331.xsd#icui_LeverageRatioLevelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_LeverageRatioLevelAxis_0e57a4c2-23bf-4e37-83b4-eb0767846d98" xlink:to="loc_icui_LeverageRatioLevelDomain_0e57a4c2-23bf-4e37-83b4-eb0767846d98_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:href="icui-20250331.xsd#icui_LeverageRatioLevelDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_LeverageRatioLevelAxis_0e57a4c2-23bf-4e37-83b4-eb0767846d98" xlink:to="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Greaterthan400to100Member_fbc58824-68c2-477e-85fd-208d3164dda9" xlink:href="icui-20250331.xsd#icui_Greaterthan400to100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_Greaterthan400to100Member_fbc58824-68c2-477e-85fd-208d3164dda9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member_072d2533-ac02-445f-8548-b7b252cd1e3d" xlink:href="icui-20250331.xsd#icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_LessThanOrEqualTo400To100ButGreaterThan300To100Member_072d2533-ac02-445f-8548-b7b252cd1e3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqual300To100ButGreaterThan250to100Member_da5920ed-2d3c-4150-ad36-278ac3f5ba33" xlink:href="icui-20250331.xsd#icui_LessThanOrEqual300To100ButGreaterThan250to100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_LessThanOrEqual300To100ButGreaterThan250to100Member_da5920ed-2d3c-4150-ad36-278ac3f5ba33" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member_5c1221c3-247b-4e89-9197-907abe7dbf15" xlink:href="icui-20250331.xsd#icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_LessThanOrEqualTo250To100ButGreaterThan200To100Member_5c1221c3-247b-4e89-9197-907abe7dbf15" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThanOrEqualTo200To100Member_86c88b6e-0733-462b-bf16-e9dbc4cc5fb3" xlink:href="icui-20250331.xsd#icui_LessThanOrEqualTo200To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_LessThanOrEqualTo200To100Member_86c88b6e-0733-462b-bf16-e9dbc4cc5fb3" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_GreaterThan275To100Member_2ed85406-2384-47b3-bcb2-64201b50f5fc" xlink:href="icui-20250331.xsd#icui_GreaterThan275To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_GreaterThan275To100Member_2ed85406-2384-47b3-bcb2-64201b50f5fc" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_LessThan275To100Member_4f4ca493-3216-4ace-8831-0f6fcf0cd529" xlink:href="icui-20250331.xsd#icui_LessThan275To100Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_LeverageRatioLevelDomain_f3c53e1b-6b45-4586-8fd4-57ffe338a27a" xlink:to="loc_icui_LessThan275To100Member_4f4ca493-3216-4ace-8831-0f6fcf0cd529" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_f06fbfd1-0ea0-40f9-828f-ec174e51b186" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioTable_b706d8b3-971e-4125-8f5e-9165ee6847e0" xlink:to="loc_srt_RangeAxis_f06fbfd1-0ea0-40f9-828f-ec174e51b186" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f06fbfd1-0ea0-40f9-828f-ec174e51b186_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_f06fbfd1-0ea0-40f9-828f-ec174e51b186" xlink:to="loc_srt_RangeMember_f06fbfd1-0ea0-40f9-828f-ec174e51b186_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_f4cf39ad-97ae-4ac8-bda8-32f622eae4e1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_f06fbfd1-0ea0-40f9-828f-ec174e51b186" xlink:to="loc_srt_RangeMember_f4cf39ad-97ae-4ac8-bda8-32f622eae4e1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ff14860e-bd21-4949-8a80-f461c4f30455" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f4cf39ad-97ae-4ac8-bda8-32f622eae4e1" xlink:to="loc_srt_MaximumMember_ff14860e-bd21-4949-8a80-f461c4f30455" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_977de9b4-ee4c-496c-91ab-cd1efd367a10" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_f4cf39ad-97ae-4ac8-bda8-32f622eae4e1" xlink:to="loc_srt_MinimumMember_977de9b4-ee4c-496c-91ab-cd1efd367a10" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginBaseRateLoans_5e8cf1b2-0720-4adb-9e39-d276179ab642" xlink:href="icui-20250331.xsd#icui_ApplicableMarginBaseRateLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:to="loc_icui_ApplicableMarginBaseRateLoans_5e8cf1b2-0720-4adb-9e39-d276179ab642" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ApplicableMarginTermSOFRLoans_40e32645-05db-43f6-861f-b060181ec5f7" xlink:href="icui-20250331.xsd#icui_ApplicableMarginTermSOFRLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:to="loc_icui_ApplicableMarginTermSOFRLoans_40e32645-05db-43f6-861f-b060181ec5f7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_4fe5493d-6de7-4f32-9fe4-df492e21d3f7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityCommitmentFeePercentage"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:to="loc_us-gaap_LineOfCreditFacilityCommitmentFeePercentage_4fe5493d-6de7-4f32-9fe4-df492e21d3f7" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans_9d852267-526d-4678-923d-73de8dbcad46" xlink:href="icui-20250331.xsd#icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ApplicableMarginBasedOnLeverageRatioLineItems_aa042cbc-a850-4968-8a84-55bbd7380ca1" xlink:to="loc_icui_TermSOFRAdjustmentInterestRateAdjustmentTermSOFRLoans_9d852267-526d-4678-923d-73de8dbcad46" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsTableDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#LongTermObligationsTableDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsTableDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_3fca8e62-64e0-4c68-b048-89ee846e3ee1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtInstrumentTable_3fca8e62-64e0-4c68-b048-89ee846e3ee1" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAxis_a69d387b-e42b-49a8-b19f-f7d24804a588" xlink:href="icui-20250331.xsd#icui_TermLoanAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3fca8e62-64e0-4c68-b048-89ee846e3ee1" xlink:to="loc_icui_TermLoanAxis_a69d387b-e42b-49a8-b19f-f7d24804a588" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_a69d387b-e42b-49a8-b19f-f7d24804a588_default" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_icui_TermLoanAxis_a69d387b-e42b-49a8-b19f-f7d24804a588" xlink:to="loc_icui_TermLoanDomain_a69d387b-e42b-49a8-b19f-f7d24804a588_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanDomain_746d2425-646d-4b1d-9816-613b1df2b1d1" xlink:href="icui-20250331.xsd#icui_TermLoanDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_icui_TermLoanAxis_a69d387b-e42b-49a8-b19f-f7d24804a588" xlink:to="loc_icui_TermLoanDomain_746d2425-646d-4b1d-9816-613b1df2b1d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanAMember_1c8aa8d6-ce62-4c78-87b0-875e9c0178f8" xlink:href="icui-20250331.xsd#icui_TermLoanAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_746d2425-646d-4b1d-9816-613b1df2b1d1" xlink:to="loc_icui_TermLoanAMember_1c8aa8d6-ce62-4c78-87b0-875e9c0178f8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_TermLoanBMember_bfe1efbe-489d-435d-b791-9bcd335a99ec" xlink:href="icui-20250331.xsd#icui_TermLoanBMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_TermLoanDomain_746d2425-646d-4b1d-9816-613b1df2b1d1" xlink:to="loc_icui_TermLoanBMember_bfe1efbe-489d-435d-b791-9bcd335a99ec" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_3fca8e62-64e0-4c68-b048-89ee846e3ee1" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_fc44f8e8-9120-4c89-867d-be9b6ec0b407" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ba1e2e2a-e529-428d-a4c0-d6c24f36eb78" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_fc44f8e8-9120-4c89-867d-be9b6ec0b407" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_29ad20fa-c0e0-47b7-9e9e-e82ea471561c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_fc44f8e8-9120-4c89-867d-be9b6ec0b407" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_29ad20fa-c0e0-47b7-9e9e-e82ea471561c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_f9c4f0aa-7609-49e5-af96-4a2474e6e26e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_f9c4f0aa-7609-49e5-af96-4a2474e6e26e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_43d5e0ec-9a20-4778-83a7-ba1151de2de0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_LineOfCreditFacilityFairValueOfAmountOutstanding_43d5e0ec-9a20-4778-83a7-ba1151de2de0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3eaf155e-1ab8-40ea-b413-59d32e554dbb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet_3eaf155e-1ab8-40ea-b413-59d32e554dbb" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_d942610f-8008-4d92-8a5f-f75034a67a79" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_d942610f-8008-4d92-8a5f-f75034a67a79" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtCurrent_30d467c4-5bbb-4388-8fa7-39b3eaa595fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtCurrent_30d467c4-5bbb-4388-8fa7-39b3eaa595fd" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtNoncurrent_81cbb6d5-9ba4-4b3c-9e3e-efe87c845f09" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtNoncurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_LongTermDebtNoncurrent_81cbb6d5-9ba4-4b3c-9e3e-efe87c845f09" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_ec88fd93-2b68-4078-91b0-592a2a36c076" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentInterestRateDuringPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_9e85245e-7cf6-43d3-b3e2-925cf0febaf6" xlink:to="loc_us-gaap_DebtInstrumentInterestRateDuringPeriod_ec88fd93-2b68-4078-91b0-592a2a36c076" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/CommitmentsandContingenciesContingencyDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#CommitmentsandContingenciesContingencyDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CommitmentsandContingenciesContingencyDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_210b6c02-b010-416e-a195-93bad6b6eccf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_210b6c02-b010-416e-a195-93bad6b6eccf" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_d3abe43a-22b1-495d-9215-59ae1518a540" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_210b6c02-b010-416e-a195-93bad6b6eccf" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_d3abe43a-22b1-495d-9215-59ae1518a540" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d3abe43a-22b1-495d-9215-59ae1518a540_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d3abe43a-22b1-495d-9215-59ae1518a540" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_d3abe43a-22b1-495d-9215-59ae1518a540_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_52b82f7a-b588-4fb3-b03f-ee3b04736afb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_BusinessAcquisitionAcquireeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_d3abe43a-22b1-495d-9215-59ae1518a540" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_52b82f7a-b588-4fb3-b03f-ee3b04736afb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_SmithsMedicalMember_0c44d06f-64d2-4552-b236-c0b29df78534" xlink:href="icui-20250331.xsd#icui_SmithsMedicalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_52b82f7a-b588-4fb3-b03f-ee3b04736afb" xlink:to="loc_icui_SmithsMedicalMember_0c44d06f-64d2-4552-b236-c0b29df78534" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignInfusionSystemSupplierMember_f6f2cfcc-094d-44b7-a0bd-5c8c4d9a4f9e" xlink:href="icui-20250331.xsd#icui_ForeignInfusionSystemSupplierMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_52b82f7a-b588-4fb3-b03f-ee3b04736afb" xlink:to="loc_icui_ForeignInfusionSystemSupplierMember_f6f2cfcc-094d-44b7-a0bd-5c8c4d9a4f9e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_InternationalDistributorMember_e92f275e-042c-4b75-a59f-54fab4393c98" xlink:href="icui-20250331.xsd#icui_InternationalDistributorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_52b82f7a-b588-4fb3-b03f-ee3b04736afb" xlink:to="loc_icui_InternationalDistributorMember_e92f275e-042c-4b75-a59f-54fab4393c98" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Contingentconsiderationgross_c647cbc3-1356-44d2-b785-37bb8b951459" xlink:href="icui-20250331.xsd#icui_Contingentconsiderationgross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:to="loc_icui_Contingentconsiderationgross_c647cbc3-1356-44d2-b785-37bb8b951459" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossST_85b20374-c391-4def-8299-bc39898d3f94" xlink:href="icui-20250331.xsd#icui_ContingentConsiderationGrossST"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:to="loc_icui_ContingentConsiderationGrossST_85b20374-c391-4def-8299-bc39898d3f94" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ContingentConsiderationGrossLT_f657524a-5937-47d2-82b5-48ae683f0dad" xlink:href="icui-20250331.xsd#icui_ContingentConsiderationGrossLT"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:to="loc_icui_ContingentConsiderationGrossLT_f657524a-5937-47d2-82b5-48ae683f0dad" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProductLiabilityAccrualComponentAmount_1ce15330-6017-4282-8d6f-0ea20fedaf2a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProductLiabilityAccrualComponentAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_36d955a0-47e6-407c-8b49-b179a2491399" xlink:to="loc_us-gaap_ProductLiabilityAccrualComponentAmount_1ce15330-6017-4282-8d6f-0ea20fedaf2a" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#EquityAccumulatedOtherComprehensiveIncomeLossDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/EquityAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_587ac711-1cf3-4ef3-b7e0-ba4e0d694904" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_587ac711-1cf3-4ef3-b7e0-ba4e0d694904" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_c4e69cf2-799b-479b-b7cf-b93833a8d28c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_587ac711-1cf3-4ef3-b7e0-ba4e0d694904" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_c4e69cf2-799b-479b-b7cf-b93833a8d28c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_c4e69cf2-799b-479b-b7cf-b93833a8d28c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c4e69cf2-799b-479b-b7cf-b93833a8d28c" xlink:to="loc_us-gaap_EquityComponentDomain_c4e69cf2-799b-479b-b7cf-b93833a8d28c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_ccce0294-82cd-4f00-8e18-83b1ee3a3a13" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_c4e69cf2-799b-479b-b7cf-b93833a8d28c" xlink:to="loc_us-gaap_EquityComponentDomain_ccce0294-82cd-4f00-8e18-83b1ee3a3a13" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_ea043770-a931-496a-b0a2-6e0e982d9a1d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_ccce0294-82cd-4f00-8e18-83b1ee3a3a13" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_ea043770-a931-496a-b0a2-6e0e982d9a1d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_11be9ce1-5896-41cf-a625-cfcc16c0bbcb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_11be9ce1-5896-41cf-a625-cfcc16c0bbcb" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_edc08283-163a-4a3a-b118-b9cb0f4730e2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_edc08283-163a-4a3a-b118-b9cb0f4730e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_9559a005-416d-4eb9-bfb8-75beabf1732d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_9559a005-416d-4eb9-bfb8-75beabf1732d" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_50244166-da56-4bff-b8ff-40dfd1cba463" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_50244166-da56-4bff-b8ff-40dfd1cba463" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_496ec843-871e-49d8-8cb7-1d87e30e8197" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_496ec843-871e-49d8-8cb7-1d87e30e8197" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax_51f2f27b-3312-432b-842c-07223e093b52" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentNetOfTax_51f2f27b-3312-432b-842c-07223e093b52" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_4ba55e72-e9a2-4dae-b612-92a175dc982d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_4ba55e72-e9a2-4dae-b612-92a175dc982d" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_e5d5585a-8b22-4738-8a4e-ef641c3222fa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationReclassificationAdjustmentFromAOCIRealizedUponSaleOrLiquidationNetOfTax_e5d5585a-8b22-4738-8a4e-ef641c3222fa" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax_0f72832a-5c92-4fe4-9158-3dadf2ca1565" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax_0f72832a-5c92-4fe4-9158-3dadf2ca1565" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_f989873e-c320-40d4-9541-4a1e26167767" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAfterTax_f989873e-c320-40d4-9541-4a1e26167767" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_72bf76f3-10e2-46da-bd48-c8987db0e1a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossReclassificationAfterTax_72bf76f3-10e2-46da-bd48-c8987db0e1a5" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_63a1eb6e-594e-4ab2-8e92-01f00c7f7e56" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax_63a1eb6e-594e-4ab2-8e92-01f00c7f7e56" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax_fd152120-fb0d-440c-adf7-ab1f3f29b147" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossDefinedBenefitPensionAndOtherPostretirementPlansNetOfTax_fd152120-fb0d-440c-adf7-ab1f3f29b147" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax_012860fd-a88a-4d21-899d-fc5b8cc99f73" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentBeforeReclassificationAdjustmentsNetOfTax_012860fd-a88a-4d21-899d-fc5b8cc99f73" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_aae65961-785a-4fa1-86b7-4c237a015be2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_47e5fe57-2ec8-45f7-b86b-975f52aba7fd" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_aae65961-785a-4fa1-86b7-4c237a015be2" xlink:type="arc" order="14"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SegmentReportingDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#SegmentReportingDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SegmentReportingDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6b03b693-66b8-4cb6-a945-8998cbddbd0d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6b03b693-66b8-4cb6-a945-8998cbddbd0d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_28185816-4d52-4458-b8a2-5fa79cda3cae" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_6b03b693-66b8-4cb6-a945-8998cbddbd0d" xlink:to="loc_srt_ConsolidationItemsAxis_28185816-4d52-4458-b8a2-5fa79cda3cae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_28185816-4d52-4458-b8a2-5fa79cda3cae_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_28185816-4d52-4458-b8a2-5fa79cda3cae" xlink:to="loc_srt_ConsolidationItemsDomain_28185816-4d52-4458-b8a2-5fa79cda3cae_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_48a6ad72-524b-4c82-959d-eca21e11f7a9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_28185816-4d52-4458-b8a2-5fa79cda3cae" xlink:to="loc_srt_ConsolidationItemsDomain_48a6ad72-524b-4c82-959d-eca21e11f7a9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_fa7c6a9a-00de-47c4-b7bd-65ba7b003a1e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_48a6ad72-524b-4c82-959d-eca21e11f7a9" xlink:to="loc_us-gaap_OperatingSegmentsMember_fa7c6a9a-00de-47c4-b7bd-65ba7b003a1e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_82d58e95-60df-4737-916c-f807896bce96" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_Revenues_82d58e95-60df-4737-916c-f807896bce96" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ManufacturingCosts_9e7bc46a-96ef-424a-a0a2-60639cf60719" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ManufacturingCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_ManufacturingCosts_9e7bc46a-96ef-424a-a0a2-60639cf60719" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InventoryRecallExpense_dbc35806-a7cb-4c41-8ea2-6192e890448b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InventoryRecallExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_InventoryRecallExpense_dbc35806-a7cb-4c41-8ea2-6192e890448b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherCostAndExpenseOperating_03a0f05a-c74e-4ff2-b425-3447582b152d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherCostAndExpenseOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_OtherCostAndExpenseOperating_03a0f05a-c74e-4ff2-b425-3447582b152d" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_0333f670-05f1-46e8-9b32-7be64a2de7ae" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SellingGeneralAndAdministrativeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_0333f670-05f1-46e8-9b32-7be64a2de7ae" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_da68cdf0-ecb8-4e24-9ab1-d12ad70cac70" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ResearchAndDevelopmentExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_da68cdf0-ecb8-4e24-9ab1-d12ad70cac70" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_Restructuringandstrategictransactionexpense_e7aef19e-93ef-47f4-a64d-d1a15dc53efc" xlink:href="icui-20250331.xsd#icui_Restructuringandstrategictransactionexpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_icui_Restructuringandstrategictransactionexpense_e7aef19e-93ef-47f4-a64d-d1a15dc53efc" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingOtherItemAmount_3815d436-0623-43e2-a23b-7506b771eb59" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingOtherItemAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_SegmentReportingOtherItemAmount_3815d436-0623-43e2-a23b-7506b771eb59" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestExpenseNonoperating_77ebe463-34a1-4b60-9c5e-e9d9f51487d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestExpenseNonoperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_InterestExpenseNonoperating_77ebe463-34a1-4b60-9c5e-e9d9f51487d7" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_bba77d6d-cc0f-485a-b289-bcec43d2e7e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeTaxExpenseBenefit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_bba77d6d-cc0f-485a-b289-bcec43d2e7e1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_NetIncomeLoss_ed8e9617-04f3-468e-a93e-d5d2b8d2b526" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_NetIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_e3f67f5b-b77a-42e0-9686-18f662bfd7b8" xlink:to="loc_us-gaap_NetIncomeLoss_ed8e9617-04f3-468e-a93e-d5d2b8d2b526" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_7023a745-2efa-4abf-b09a-fab62ca39742" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_4a14e812-5e06-4091-b685-e9f114a2b838" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_7023a745-2efa-4abf-b09a-fab62ca39742" xlink:to="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_4a14e812-5e06-4091-b685-e9f114a2b838" xlink:type="arc" order="2" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_770f0484-80d7-4c08-83c2-c539e1a09259" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRevenuesFromExternalCustomersAndLongLivedAssetsTable_4a14e812-5e06-4091-b685-e9f114a2b838" xlink:to="loc_srt_StatementGeographicalAxis_770f0484-80d7-4c08-83c2-c539e1a09259" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_770f0484-80d7-4c08-83c2-c539e1a09259_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_770f0484-80d7-4c08-83c2-c539e1a09259" xlink:to="loc_srt_SegmentGeographicalDomain_770f0484-80d7-4c08-83c2-c539e1a09259_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_770f0484-80d7-4c08-83c2-c539e1a09259" xlink:to="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CR_90095742-0fe2-40f8-8dd6-2ffe1e5adc76" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_CR"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_CR_90095742-0fe2-40f8-8dd6-2ffe1e5adc76" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_MX_3b39bd03-6c1e-4d5a-bb19-9fd51c0335c4" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_MX"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_MX_3b39bd03-6c1e-4d5a-bb19-9fd51c0335c4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_OtherLATAMMember_7c7cc8bd-a36e-4d6b-be0e-c839e8e00b78" xlink:href="icui-20250331.xsd#icui_OtherLATAMMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_icui_OtherLATAMMember_7c7cc8bd-a36e-4d6b-be0e-c839e8e00b78" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CA_eaead133-ba7b-43b6-b067-42c288b2e5e6" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_CA"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_CA_eaead133-ba7b-43b6-b067-42c288b2e5e6" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_IT_916a057f-2b69-4416-83a8-26dbcf099c94" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_IT"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_IT_916a057f-2b69-4416-83a8-26dbcf099c94" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_ES_79198910-0ac1-479b-b66e-6702b1daa863" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_ES"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_ES_79198910-0ac1-479b-b66e-6702b1daa863" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_CZ_42dde5ae-5288-43e0-888e-e9e53bef3efd" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_CZ"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_CZ_42dde5ae-5288-43e0-888e-e9e53bef3efd" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_EuropeMember_9a39019c-bce0-43fa-b838-98d9c32ac02d" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_EuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_srt_EuropeMember_9a39019c-bce0-43fa-b838-98d9c32ac02d" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_AsiaPacificMember_62c317d1-5954-40f0-a5dc-ae98dc33df68" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_AsiaPacificMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_srt_AsiaPacificMember_62c317d1-5954-40f0-a5dc-ae98dc33df68" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_icui_ForeignMember_7b8a6c6a-d53d-4dfe-b12e-7e72a647ea8a" xlink:href="icui-20250331.xsd#icui_ForeignMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_icui_ForeignMember_7b8a6c6a-d53d-4dfe-b12e-7e72a647ea8a" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_30c44f2d-4827-481e-945e-655db67c5102" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_fb44dd07-00e4-4738-be0d-d47baa20506c" xlink:to="loc_country_US_30c44f2d-4827-481e-945e-655db67c5102" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_32e6f6b5-c58b-41b4-a082-c0201ef3f74a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PropertyPlantAndEquipmentGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesFromExternalCustomersAndLongLivedAssetsLineItems_7023a745-2efa-4abf-b09a-fab62ca39742" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_32e6f6b5-c58b-41b4-a082-c0201ef3f74a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsDetails" xlink:type="simple" xlink:href="icui-20250331.xsd#SubsequentEventsDetails"/>
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventLineItems_5975dda4-e2eb-4306-86f2-0c6a9d7f226f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTable_f2da87af-5ba5-4478-84df-41756e76bb37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_5975dda4-e2eb-4306-86f2-0c6a9d7f226f" xlink:to="loc_us-gaap_SubsequentEventTable_f2da87af-5ba5-4478-84df-41756e76bb37" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_1505e6d5-0143-4130-9db4-5da29c43846b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_f2da87af-5ba5-4478-84df-41756e76bb37" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_1505e6d5-0143-4130-9db4-5da29c43846b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_1505e6d5-0143-4130-9db4-5da29c43846b_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1505e6d5-0143-4130-9db4-5da29c43846b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_1505e6d5-0143-4130-9db4-5da29c43846b_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_807b5dcb-976a-44c4-8b33-397b5a30e0a3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_1505e6d5-0143-4130-9db4-5da29c43846b" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_807b5dcb-976a-44c4-8b33-397b5a30e0a3" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SubsequentEventMember_10cd30b7-b0b4-4121-8315-5ce56d1b68ea" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SubsequentEventMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_807b5dcb-976a-44c4-8b33-397b5a30e0a3" xlink:to="loc_us-gaap_SubsequentEventMember_10cd30b7-b0b4-4121-8315-5ce56d1b68ea" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates_df9597e4-8394-4a11-8dba-153e8296b130" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_5975dda4-e2eb-4306-86f2-0c6a9d7f226f" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfInterestInSubsidiariesAndAffiliates_df9597e4-8394-4a11-8dba-153e8296b130" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EarlyRepaymentOfSeniorDebt_6f86cd81-46a4-482a-b4b2-a78ebcd20ed8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EarlyRepaymentOfSeniorDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_5975dda4-e2eb-4306-86f2-0c6a9d7f226f" xlink:to="loc_us-gaap_EarlyRepaymentOfSeniorDebt_6f86cd81-46a4-482a-b4b2-a78ebcd20ed8" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="simple" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-roles-2024.xsd#eedm"/>
  <link:definitionLink xlink:role="http://fasb.org/us-gaap/role/eedm/ExtensibleEnumerationLists" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LiabilitiesCurrentAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccruedLiabilitiesCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent" xlink:type="arc" order="41"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeStatementAbstract" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeStatementAbstract"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementAbstract" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:type="arc" order="691"/>
  </link:definitionLink>
</link:linkbase>
