<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:href="icui-20200331.xsd#AccruedLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesLongTermLiabilitiesDetails" xlink:href="icui-20200331.xsd#AccruedLiabilitiesLongTermLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesNotes" xlink:href="icui-20200331.xsd#AccruedLiabilitiesNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/AccruedLiabilitiesTables" xlink:href="icui-20200331.xsd#AccruedLiabilitiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/BasisOfPresentation" xlink:href="icui-20200331.xsd#BasisOfPresentation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CollaborativeAndOtherArrangementsDetails" xlink:href="icui-20200331.xsd#CollaborativeAndOtherArrangementsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CollaborativeAndOtherArrangementsNotes" xlink:href="icui-20200331.xsd#CollaborativeAndOtherArrangementsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CollaborativeAndOtherArrangementsTables" xlink:href="icui-20200331.xsd#CollaborativeAndOtherArrangementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CommitmentsAndContingencies" xlink:href="icui-20200331.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CommitmentsAndContingenciesContingencyDetails" xlink:href="icui-20200331.xsd#CommitmentsAndContingenciesContingencyDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedBalanceSheets" xlink:href="icui-20200331.xsd#CondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:href="icui-20200331.xsd#CondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:href="icui-20200331.xsd#CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsOfIncome" xlink:href="icui-20200331.xsd#CondensedConsolidatedStatementsOfIncome" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/CondensedConsolidatedStatementsOfStockholdersEquityStatement" xlink:href="icui-20200331.xsd#CondensedConsolidatedStatementsOfStockholdersEquityStatement" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DeiDocument" xlink:href="icui-20200331.xsd#DeiDocument" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesAmountsAffectingConsolidatedStatementsOfIncomeDetails" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesAmountsAffectingConsolidatedStatementsOfIncomeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesCashFlowHedgeActivityIncludedInAccumulatedOtherComprehensiveIncomeLossDetails" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesCashFlowHedgeActivityIncludedInAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesFvOfDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesFvOfDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsDetails" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsNotes" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/DerivativeFinancialInstrumentsTables" xlink:href="icui-20200331.xsd#DerivativeFinancialInstrumentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurement" xlink:href="icui-20200331.xsd#FairValueMeasurement" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationHospiraDetails" xlink:href="icui-20200331.xsd#FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationHospiraDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationPursuitDetails" xlink:href="icui-20200331.xsd#FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationPursuitDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputsDetails" xlink:href="icui-20200331.xsd#FairValueMeasurementFairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementDetails" xlink:href="icui-20200331.xsd#FairValueMeasurementFairValueMeasurementDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementsRecurringBasisDetails" xlink:href="icui-20200331.xsd#FairValueMeasurementFairValueMeasurementsRecurringBasisDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/FairValueMeasurementTables" xlink:href="icui-20200331.xsd#FairValueMeasurementTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssets5YearAmortizationDetails" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssets5YearAmortizationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssetsGoodwillTableDetails" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssetsGoodwillTableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssetsIntangiblesTableDetails" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssetsIntangiblesTableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssetsNotes" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssetsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssetsTables" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/GoodwillAndIntangibleAssetsTextDetails" xlink:href="icui-20200331.xsd#GoodwillAndIntangibleAssetsTextDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxes" xlink:href="icui-20200331.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/IncomeTaxesEffectiveTaxRateDetails" xlink:href="icui-20200331.xsd#IncomeTaxesEffectiveTaxRateDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/Inventories" xlink:href="icui-20200331.xsd#Inventories" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InventoriesDetails" xlink:href="icui-20200331.xsd#InventoriesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InventoriesTables" xlink:href="icui-20200331.xsd#InventoriesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InvestmentSecuritiesDetails" xlink:href="icui-20200331.xsd#InvestmentSecuritiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InvestmentSecuritiesNotes" xlink:href="icui-20200331.xsd#InvestmentSecuritiesNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InvestmentSecuritiesTableDetails" xlink:href="icui-20200331.xsd#InvestmentSecuritiesTableDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/InvestmentSecuritiesTables" xlink:href="icui-20200331.xsd#InvestmentSecuritiesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesAssetsAndLiabilitiesLesseeDetails" xlink:href="icui-20200331.xsd#LeasesAssetsAndLiabilitiesLesseeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesCashFlowOperatingActivitiesLesseeDetails" xlink:href="icui-20200331.xsd#LeasesCashFlowOperatingActivitiesLesseeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesDetails" xlink:href="icui-20200331.xsd#LeasesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesMaturityDetails" xlink:href="icui-20200331.xsd#LeasesMaturityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesMaturityTables" xlink:href="icui-20200331.xsd#LeasesMaturityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesNotes" xlink:href="icui-20200331.xsd#LeasesNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesSupplementalBalanceSheetTables" xlink:href="icui-20200331.xsd#LeasesSupplementalBalanceSheetTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesSupplementalCashFlowTables" xlink:href="icui-20200331.xsd#LeasesSupplementalCashFlowTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesTables" xlink:href="icui-20200331.xsd#LeasesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LeasesTextDetails" xlink:href="icui-20200331.xsd#LeasesTextDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsDetails" xlink:href="icui-20200331.xsd#LongTermObligationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsNotes" xlink:href="icui-20200331.xsd#LongTermObligationsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/LongTermObligationsTables" xlink:href="icui-20200331.xsd#LongTermObligationsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NetIncomePerShare" xlink:href="icui-20200331.xsd#NetIncomePerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NetIncomePerShareDetails" xlink:href="icui-20200331.xsd#NetIncomePerShareDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NetIncomePerShareDetails1" xlink:href="icui-20200331.xsd#NetIncomePerShareDetails1" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NetIncomePerShareTables" xlink:href="icui-20200331.xsd#NetIncomePerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NewAccountingPronouncements" xlink:href="icui-20200331.xsd#NewAccountingPronouncements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/NewAccountingPronouncementsNewAccountingPronouncementsAdoptedPolicies" xlink:href="icui-20200331.xsd#NewAccountingPronouncementsNewAccountingPronouncementsAdoptedPolicies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsNotes" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsPrepaidsAndOtherAssetsDetails" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsPrepaidsAndOtherAssetsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsRelatedPartyReceivableDetailsDetails" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsRelatedPartyReceivableDetailsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsRelatedPartyTextDetails" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsRelatedPartyTextDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsTables" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsTextDetails" xlink:href="icui-20200331.xsd#PrepaidsAndOtherCurrentAssetsTextDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PropertyAndEquipment" xlink:href="icui-20200331.xsd#PropertyAndEquipment" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PropertyAndEquipmentDetails" xlink:href="icui-20200331.xsd#PropertyAndEquipmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PropertyAndEquipmentTables" xlink:href="icui-20200331.xsd#PropertyAndEquipmentTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/PropertyAndEquipmentTextDetails" xlink:href="icui-20200331.xsd#PropertyAndEquipmentTextDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationDetails" xlink:href="icui-20200331.xsd#RestructuringStrategicTransactionAndIntegrationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationNotes" xlink:href="icui-20200331.xsd#RestructuringStrategicTransactionAndIntegrationNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationRestructuringStrategicTransactionAndIntegrationDetails" xlink:href="icui-20200331.xsd#RestructuringStrategicTransactionAndIntegrationRestructuringStrategicTransactionAndIntegrationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationStrategicTransactionAndIntegrationDetails" xlink:href="icui-20200331.xsd#RestructuringStrategicTransactionAndIntegrationStrategicTransactionAndIntegrationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationTables" xlink:href="icui-20200331.xsd#RestructuringStrategicTransactionAndIntegrationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:href="icui-20200331.xsd#RevenueContractLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDetails" xlink:href="icui-20200331.xsd#RevenueDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenueByGeographyDetails" xlink:href="icui-20200331.xsd#RevenueDisaggregatedRevenueByGeographyDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueDisaggregatedRevenueByProductLineDetails" xlink:href="icui-20200331.xsd#RevenueDisaggregatedRevenueByProductLineDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueNotes" xlink:href="icui-20200331.xsd#RevenueNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/RevenueTables" xlink:href="icui-20200331.xsd#RevenueTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityAccumulatedOtherComprehensiveIncomeDetails" xlink:href="icui-20200331.xsd#StockholdersEquityAccumulatedOtherComprehensiveIncomeDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityDetails" xlink:href="icui-20200331.xsd#StockholdersEquityDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityNotes" xlink:href="icui-20200331.xsd#StockholdersEquityNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/StockholdersEquityTables" xlink:href="icui-20200331.xsd#StockholdersEquityTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsDetails" xlink:href="icui-20200331.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsNotes" xlink:href="icui-20200331.xsd#SubsequentEventsNotes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.icumed.com/role/SubsequentEventsTables" xlink:href="icui-20200331.xsd#SubsequentEventsTables" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesLongTermLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/AccruedLiabilitiesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/BasisOfPresentation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/CollaborativeAndOtherArrangementsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/CollaborativeAndOtherArrangementsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/CollaborativeAndOtherArrangementsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/CommitmentsAndContingenciesContingencyDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionContingentConsiderationLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_DE31002714CBF8F6D448C6F38710B3B5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_BE0DF4F4EA1CF66BBC97C6F3870F1365" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_DE31002714CBF8F6D448C6F38710B3B5" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_BE0DF4F4EA1CF66BBC97C6F3870F1365" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_FC081B198E5C61ED85B4C6F3874B7579" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionContingentConsiderationTable_BE0DF4F4EA1CF66BBC97C6F3870F1365" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_FC081B198E5C61ED85B4C6F3874B7579" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5B186860B9CE9A33AFE9C6F388F7D107_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_FC081B198E5C61ED85B4C6F3874B7579" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5B186860B9CE9A33AFE9C6F388F7D107_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5B186860B9CE9A33AFE9C6F388F7D107" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_FC081B198E5C61ED85B4C6F3874B7579" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5B186860B9CE9A33AFE9C6F388F7D107" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_PursuitVascularInc.Member" xlink:label="loc_icui_PursuitVascularInc.Member_F00248EC6667681D738DC6F3876B20C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_5B186860B9CE9A33AFE9C6F388F7D107" xlink:to="loc_icui_PursuitVascularInc.Member_F00248EC6667681D738DC6F3876B20C5" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Contingentconsiderationgross" xlink:label="loc_icui_Contingentconsiderationgross_99E5453B04191B7594CFC6F3872A5746" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionContingentConsiderationLineItems_DE31002714CBF8F6D448C6F38710B3B5" xlink:to="loc_icui_Contingentconsiderationgross_99E5453B04191B7594CFC6F3872A5746" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1AFCB819FE8D39BC7794EB75839BB216" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_StatementTable_1AFCB819FE8D39BC7794EB75839BB216" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementScenarioAxis" xlink:label="loc_srt_StatementScenarioAxis_F8D889BDDCC5FA364CCCEB75839C9919" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1AFCB819FE8D39BC7794EB75839BB216" xlink:to="loc_srt_StatementScenarioAxis_F8D889BDDCC5FA364CCCEB75839C9919" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_82FA0F10127220167142EB75839DCFFC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_F8D889BDDCC5FA364CCCEB75839C9919" xlink:to="loc_srt_ScenarioUnspecifiedDomain_82FA0F10127220167142EB75839DCFFC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_82FA0F10127220167142EB75839DCFFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_F8D889BDDCC5FA364CCCEB75839C9919" xlink:to="loc_srt_ScenarioUnspecifiedDomain_82FA0F10127220167142EB75839DCFFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsAbstract" xlink:label="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsCurrentAbstract" xlink:label="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_F93A8D97475EA5744985EB75839E1470" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_F93A8D97475EA5744985EB75839E1470" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesCurrent_5D6B8DC3FD07D08CD7D3EB75839F6FCE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesCurrent_5D6B8DC3FD07D08CD7D3EB75839F6FCE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashCashEquivalentsAndShortTermInvestments" xlink:label="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_3CFADED1EA277824E645EB75839FD2AC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_CashCashEquivalentsAndShortTermInvestments_3CFADED1EA277824E645EB75839FD2AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsReceivableNetCurrent" xlink:label="loc_us-gaap_AccountsReceivableNetCurrent_5ACEAFA9509D1615EA69EB75839FAD63" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_AccountsReceivableNetCurrent_5ACEAFA9509D1615EA69EB75839FAD63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InventoryNet" xlink:label="loc_us-gaap_InventoryNet_D8B0111C308EEE1623A3EB75839FA69D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_InventoryNet_D8B0111C308EEE1623A3EB75839FA69D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidTaxes" xlink:label="loc_us-gaap_PrepaidTaxes_A740D98FDAAC40B2EF56EB7583A092F4" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_PrepaidTaxes_A740D98FDAAC40B2EF56EB7583A092F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpenseAndOtherAssetsCurrent" xlink:label="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_A637F72F0D22B87B7A8EEB7583A07C9C" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_PrepaidExpenseAndOtherAssetsCurrent_A637F72F0D22B87B7A8EEB7583A07C9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="loc_us-gaap_AssetsCurrent_230376C63A943051D31FEB7583A0C7EC" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsCurrentAbstract_F811BB5B03D84F1BF46BEB75839EFAD2" xlink:to="loc_us-gaap_AssetsCurrent_230376C63A943051D31FEB7583A0C7EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_42E0FCDFBA7822668469EB7583A022C7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_42E0FCDFBA7822668469EB7583A022C7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="loc_us-gaap_OperatingLeaseRightOfUseAsset_65ED9B90D6053CAB2F70EB7583A05326" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_OperatingLeaseRightOfUseAsset_65ED9B90D6053CAB2F70EB7583A05326" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_C0E9B388A51CAF216768EB7583A00E8C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_Goodwill_C0E9B388A51CAF216768EB7583A00E8C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_BCF2AEA9BFF2B915DE84EB7583A1BE8D" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_BCF2AEA9BFF2B915DE84EB7583A1BE8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredIncomeTaxAssetsNet" xlink:label="loc_us-gaap_DeferredIncomeTaxAssetsNet_37A03FF11716AFAA1623EB7583A190F2" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_DeferredIncomeTaxAssetsNet_37A03FF11716AFAA1623EB7583A190F2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherAssetsNoncurrent" xlink:label="loc_us-gaap_OtherAssetsNoncurrent_008EEEFA6DF32D23E3EBEB7583A11C3A" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_OtherAssetsNoncurrent_008EEEFA6DF32D23E3EBEB7583A11C3A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_5FC63E9693185AD9785FEB7583A127B1" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AssetsAbstract_0CEF299EAD36C76F7BEFEB75839E8508" xlink:to="loc_us-gaap_Assets_5FC63E9693185AD9785FEB7583A127B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="loc_us-gaap_AccountsPayableCurrent_508AFEF556B67153BBF7EB7583A25ACA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:to="loc_us-gaap_AccountsPayableCurrent_508AFEF556B67153BBF7EB7583A25ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="loc_us-gaap_AccruedLiabilitiesCurrent_7D04D72D102378F31FD4EB7583A2F8B3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:to="loc_us-gaap_AccruedLiabilitiesCurrent_7D04D72D102378F31FD4EB7583A2F8B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedIncomeTaxesCurrent" xlink:label="loc_us-gaap_AccruedIncomeTaxesCurrent_668BE7CA4D88CB01B5CBEB7583A2E060" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:to="loc_us-gaap_AccruedIncomeTaxesCurrent_668BE7CA4D88CB01B5CBEB7583A2E060" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtCurrent" xlink:label="loc_us-gaap_LongTermDebtCurrent_2A17F48C210323F13140EB7583A2EF12" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:to="loc_us-gaap_LongTermDebtCurrent_2A17F48C210323F13140EB7583A2EF12" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="loc_us-gaap_LiabilitiesCurrent_BAC8C78FE25B70534A5EEB7583A334E3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesCurrentAbstract_8F631F1FA8F610A1A117EB7583A198C6" xlink:to="loc_us-gaap_LiabilitiesCurrent_BAC8C78FE25B70534A5EEB7583A334E3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_BDE8D8FC0AA8B53A6CA0EB7583A30A8D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_BDE8D8FC0AA8B53A6CA0EB7583A30A8D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="loc_us-gaap_OtherLiabilitiesNoncurrent_0330A2D4EBF1D8FD072AEB7583A33F3B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_OtherLiabilitiesNoncurrent_0330A2D4EBF1D8FD072AEB7583A33F3B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredIncomeTaxLiabilitiesNet" xlink:label="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_46503500DCDA891461F5EB7583A3C140" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_DeferredIncomeTaxLiabilitiesNet_46503500DCDA891461F5EB7583A3C140" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedIncomeTaxesNoncurrent" xlink:label="loc_us-gaap_AccruedIncomeTaxesNoncurrent_29949C8170FF52B8084AEB7583A37E0C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_AccruedIncomeTaxesNoncurrent_29949C8170FF52B8084AEB7583A37E0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="loc_us-gaap_CommitmentsAndContingencies_73462A4261F7E4E11EFBEB7583A3A42D" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_CommitmentsAndContingencies_73462A4261F7E4E11EFBEB7583A3A42D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue" xlink:label="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_BECB34CBF121F0B27CA3EB7583A4EC7B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_ConvertiblePreferredStockNonredeemableOrRedeemableIssuerOptionValue_BECB34CBF121F0B27CA3EB7583A4EC7B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockValue" xlink:label="loc_us-gaap_CommonStockValue_34D795ABC75BDBE11B32EB7583A4ACBA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_CommonStockValue_34D795ABC75BDBE11B32EB7583A4ACBA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="loc_us-gaap_AdditionalPaidInCapitalCommonStock_CC544A222406DEEB48AAEB7583A428F8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_AdditionalPaidInCapitalCommonStock_CC544A222406DEEB48AAEB7583A428F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockValue" xlink:label="loc_us-gaap_TreasuryStockValue_0518AB09077CCE7D950EEB7583A420F4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_TreasuryStockValue_0518AB09077CCE7D950EEB7583A420F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsAccumulatedDeficit" xlink:label="loc_us-gaap_RetainedEarningsAccumulatedDeficit_F031BA6F4B4361590537EB7583A5AAF3" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_RetainedEarningsAccumulatedDeficit_F031BA6F4B4361590537EB7583A5AAF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7C613A8C27C0B12A7FC2EB7583A5C851" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_7C613A8C27C0B12A7FC2EB7583A5C851" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_152EA7F565B810450F3BEB7583A5285F" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterestAbstract_746B7462A2E9BE81941DEB7583A4E033" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_152EA7F565B810450F3BEB7583A5285F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="loc_us-gaap_LiabilitiesAndStockholdersEquity_CD59E85EF99CF24ED746EB7583A5D9A2" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LiabilitiesAndStockholdersEquityAbstract_FD03CA8BEC40DD962169EB7583A1F699" xlink:to="loc_us-gaap_LiabilitiesAndStockholdersEquity_CD59E85EF99CF24ED746EB7583A5D9A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_6738131E3AF07E000FA1EB7583A55C83" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivableCurrent_6738131E3AF07E000FA1EB7583A55C83" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_PreferredStockParOrStatedValuePerShare_EE7B506CBED3B4CEA4B7EB7583A527D4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_PreferredStockParOrStatedValuePerShare_EE7B506CBED3B4CEA4B7EB7583A527D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockSharesAuthorized" xlink:label="loc_us-gaap_PreferredStockSharesAuthorized_AB65AC08FC17D368D2F1EB7583A6C7F4" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_PreferredStockSharesAuthorized_AB65AC08FC17D368D2F1EB7583A6C7F4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockSharesIssued" xlink:label="loc_us-gaap_PreferredStockSharesIssued_96A67CF0315151CCC61DEB7583A6EE81" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_PreferredStockSharesIssued_96A67CF0315151CCC61DEB7583A6EE81" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PreferredStockSharesOutstanding" xlink:label="loc_us-gaap_PreferredStockSharesOutstanding_FBCAA65553FE23FFC053EB7583A62F29" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_PreferredStockSharesOutstanding_FBCAA65553FE23FFC053EB7583A62F29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="loc_us-gaap_CommonStockParOrStatedValuePerShare_4D1F0CFB372AF27564A3EB7583A6C39D" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_CommonStockParOrStatedValuePerShare_4D1F0CFB372AF27564A3EB7583A6C39D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesAuthorized" xlink:label="loc_us-gaap_CommonStockSharesAuthorized_F8C36CA1D9FB8C20611AEB7583A6EC34" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_CommonStockSharesAuthorized_F8C36CA1D9FB8C20611AEB7583A6EC34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesIssued" xlink:label="loc_us-gaap_CommonStockSharesIssued_4CD471AD55485D504E03EB7583A6FF62" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_CommonStockSharesIssued_4CD471AD55485D504E03EB7583A6FF62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_7C2F8FA5AEA2577671A6EB7583A7911A" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_7C2F8FA5AEA2577671A6EB7583A7911A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockShares" xlink:label="loc_us-gaap_TreasuryStockShares_EFA63C3C64D087FEEBD8EB7583A7AD97" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6CDFDE13826477C71A93EB75839D3B36" xlink:to="loc_us-gaap_TreasuryStockShares_EFA63C3C64D087FEEBD8EB7583A7AD97" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_CDA4376064E98A009A1AAD21AE6085F1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_StatementTable_CDA4376064E98A009A1AAD21AE6085F1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_02C6604BF01FA98635CFAD21AE60F47E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_CDA4376064E98A009A1AAD21AE6085F1" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_02C6604BF01FA98635CFAD21AE60F47E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_FB1034685E398E964B3AAD21AE60B0B8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_02C6604BF01FA98635CFAD21AE60F47E" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_FB1034685E398E964B3AAD21AE60B0B8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_FB1034685E398E964B3AAD21AE60B0B8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_02C6604BF01FA98635CFAD21AE60F47E" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_FB1034685E398E964B3AAD21AE60B0B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementScenarioAxis" xlink:label="loc_srt_StatementScenarioAxis_868917216722BC3B2330AD21AE606C6C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_CDA4376064E98A009A1AAD21AE6085F1" xlink:to="loc_srt_StatementScenarioAxis_868917216722BC3B2330AD21AE606C6C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_9E1F5A390FCB23B05D4BAD21AE6079F9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_868917216722BC3B2330AD21AE606C6C" xlink:to="loc_srt_ScenarioUnspecifiedDomain_9E1F5A390FCB23B05D4BAD21AE6079F9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_9E1F5A390FCB23B05D4BAD21AE6079F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_868917216722BC3B2330AD21AE606C6C" xlink:to="loc_srt_ScenarioUnspecifiedDomain_9E1F5A390FCB23B05D4BAD21AE6079F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_ECEE5914FEF5B1E1F397AD21AE60ED4C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_ECEE5914FEF5B1E1F397AD21AE60ED4C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_852140832AE3DB4270EDAD21AE6094D2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_ECEE5914FEF5B1E1F397AD21AE60ED4C" xlink:to="loc_us-gaap_ProfitLoss_852140832AE3DB4270EDAD21AE6094D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_ECEE5914FEF5B1E1F397AD21AE60ED4C" xlink:to="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_15C27C662B5C29AB6D6BAD21AE602866" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_15C27C662B5C29AB6D6BAD21AE602866" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Operatingleaserightofuseassetamortization" xlink:label="loc_icui_Operatingleaserightofuseassetamortization_E272F6EFAC0F9B3FA775AD21AE603E11" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_icui_Operatingleaserightofuseassetamortization_E272F6EFAC0F9B3FA775AD21AE603E11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProvisionForDoubtfulAccounts" xlink:label="loc_us-gaap_ProvisionForDoubtfulAccounts_35947E312B5B4FDA6070AD21AE60958D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_ProvisionForDoubtfulAccounts_35947E312B5B4FDA6070AD21AE60958D" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_ProvisionForWarrantyAndReturns" xlink:label="loc_icui_ProvisionForWarrantyAndReturns_FCB6DDA331A3DE750D51AD21AE604726" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_icui_ProvisionForWarrantyAndReturns_FCB6DDA331A3DE750D51AD21AE604726" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_1856FBDCC7E0EDE7CAFAAD21AE6041EE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_ShareBasedCompensation_1856FBDCC7E0EDE7CAFAAD21AE6041EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:label="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_2AF065DBCEBA36D58327AD21AE60173C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_GainLossOnSaleOfPropertyPlantEquipment_2AF065DBCEBA36D58327AD21AE60173C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentIncomeAmortizationOfPremium" xlink:label="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_81C951AE8908E8C26ED0AD21AE60228B" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_InvestmentIncomeAmortizationOfPremium_81C951AE8908E8C26ED0AD21AE60228B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationOfFinancingCosts" xlink:label="loc_us-gaap_AmortizationOfFinancingCosts_D25EF68AC77F2E1214CEAD21AE60BDD0" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_AmortizationOfFinancingCosts_D25EF68AC77F2E1214CEAD21AE60BDD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_60BC79889732E96776F6AD21AE60C5F3" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_60BC79889732E96776F6AD21AE60C5F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InventoryRecallExpense" xlink:label="loc_us-gaap_InventoryRecallExpense_946229989ED231F29556AD21AE60A0C7" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_InventoryRecallExpense_946229989ED231F29556AD21AE60A0C7" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Sparepartsusage" xlink:label="loc_icui_Sparepartsusage_B3452B89EAFBFC9B5F81AD21AE60BFC1" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_icui_Sparepartsusage_B3452B89EAFBFC9B5F81AD21AE60BFC1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoncashIncomeExpense" xlink:label="loc_us-gaap_OtherNoncashIncomeExpense_B7692944D767D587FBD1AD21AE60EF34" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_OtherNoncashIncomeExpense_B7692944D767D587FBD1AD21AE60EF34" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_DB5581DC6E502578D77BAD21AE607A9C" xlink:to="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_1EB4649515FD5789347DAD21AE60C86D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsReceivable_1EB4649515FD5789347DAD21AE60C86D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInInventories" xlink:label="loc_us-gaap_IncreaseDecreaseInInventories_3DE9E08889B19CF6E109AD21AE60FD74" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInInventories_3DE9E08889B19CF6E109AD21AE60FD74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_55336E8F3B974887CFAEAD21AE605DC5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_55336E8F3B974887CFAEAD21AE605DC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInOtherOperatingAssets" xlink:label="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_484208827CE2D680602CAD21AE60CED6" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInOtherOperatingAssets_484208827CE2D680602CAD21AE60CED6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayable" xlink:label="loc_us-gaap_IncreaseDecreaseInAccountsPayable_18892E72E4A1FA8C8D1EAD21AE609BDB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInAccountsPayable_18892E72E4A1FA8C8D1EAD21AE609BDB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInAccruedLiabilities" xlink:label="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_9A8F02A488BDCCC5CBE2AD21AE60E7B8" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_us-gaap_IncreaseDecreaseInAccruedLiabilities_9A8F02A488BDCCC5CBE2AD21AE60E7B8" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes" xlink:label="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_B83B49928A0BEA198D31AD21AE60673F" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_859D42233BB171FAAE02AD21AE60A04F" xlink:to="loc_icui_IncreaseDecreaseinincometaxesincludingexcesstaxbenefitsanddeferredincometaxes_B83B49928A0BEA198D31AD21AE60673F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_D6DB1ED590E696052262AD21AE600EAA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_ECEE5914FEF5B1E1F397AD21AE60ED4C" xlink:to="loc_us-gaap_NetCashProvidedByUsedInOperatingActivities_D6DB1ED590E696052262AD21AE600EAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_62DE465CA4B2B1F10364AD21AE602360" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_62DE465CA4B2B1F10364AD21AE602360" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_2073D2CFB30F2DDADE3FAD21AE6067FA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_2073D2CFB30F2DDADE3FAD21AE6067FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireIntangibleAssets" xlink:label="loc_us-gaap_PaymentsToAcquireIntangibleAssets_C298E33F3A2A0653DA0EAD21AE6098C4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_PaymentsToAcquireIntangibleAssets_C298E33F3A2A0653DA0EAD21AE6098C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireMarketableSecurities" xlink:label="loc_us-gaap_PaymentsToAcquireMarketableSecurities_4A22678C5E73AEC65A71AD21AE607986" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_PaymentsToAcquireMarketableSecurities_4A22678C5E73AEC65A71AD21AE607986" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities" xlink:label="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_BAD8CCE15BDC547894C0AD21AE60DB3E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities_BAD8CCE15BDC547894C0AD21AE60DB3E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_2E0F65A2583D99ECC549AD21AE608AB6" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_7984B192707DE95701B1AD21AE602487" xlink:to="loc_us-gaap_NetCashProvidedByUsedInInvestingActivities_2E0F65A2583D99ECC549AD21AE608AB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_400794896C769163AA6CAD21AE603DB7" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_400794896C769163AA6CAD21AE603DB7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromStockOptionsExercised" xlink:label="loc_us-gaap_ProceedsFromStockOptionsExercised_70BC7DC97AE834000533AD21AE60B785" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_400794896C769163AA6CAD21AE603DB7" xlink:to="loc_us-gaap_ProceedsFromStockOptionsExercised_70BC7DC97AE834000533AD21AE60B785" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_B0599EC748253BF1FBCBAD21AE70B970" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_400794896C769163AA6CAD21AE603DB7" xlink:to="loc_us-gaap_PaymentsRelatedToTaxWithholdingForShareBasedCompensation_B0599EC748253BF1FBCBAD21AE70B970" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_391A23DF78CF0B475D23AD21AE70D9A9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_400794896C769163AA6CAD21AE603DB7" xlink:to="loc_us-gaap_NetCashProvidedByUsedInFinancingActivities_391A23DF78CF0B475D23AD21AE70D9A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProceedsFromLinesOfCredit" xlink:label="loc_us-gaap_ProceedsFromLinesOfCredit_C397D77227AA6A96D6B1AD21AE70943F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_ProceedsFromLinesOfCredit_C397D77227AA6A96D6B1AD21AE70943F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_E6C655C7608C0213DCDEAD21AE70FF48" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_E6C655C7608C0213DCDEAD21AE70FF48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_6392E26F6C2E6081B7AFAD389645803E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_6392E26F6C2E6081B7AFAD389645803E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:label="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_D092E20320A9778D0794AD21AE705432" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_CashAndCashEquivalentsAtCarryingValue_D092E20320A9778D0794AD21AE705432" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncashInvestingAndFinancingItemsAbstract" xlink:label="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_C42A885D645EF6D9B7A4AD21AE706913" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_NoncashInvestingAndFinancingItemsAbstract_C42A885D645EF6D9B7A4AD21AE706913" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CapitalExpendituresIncurredButNotYetPaid" xlink:label="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_8D100A388081D0FD00E6AD21AE70EB1A" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_E90ABC6E038DC70079EBAD21AE60977F" xlink:to="loc_us-gaap_CapitalExpendituresIncurredButNotYetPaid_8D100A388081D0FD00E6AD21AE70EB1A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsOfComprehensiveIncome" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_B2DDABAB6731E700DCABEB761BF484AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_StatementTable_B2DDABAB6731E700DCABEB761BF484AC" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementScenarioAxis" xlink:label="loc_srt_StatementScenarioAxis_583E7E3205C4873D4827EB761BF560C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_B2DDABAB6731E700DCABEB761BF484AC" xlink:to="loc_srt_StatementScenarioAxis_583E7E3205C4873D4827EB761BF560C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_E6C43B6CF66A814FE6F7EB761BF5013F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementScenarioAxis_583E7E3205C4873D4827EB761BF560C3" xlink:to="loc_srt_ScenarioUnspecifiedDomain_E6C43B6CF66A814FE6F7EB761BF5013F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ScenarioUnspecifiedDomain" xlink:label="loc_srt_ScenarioUnspecifiedDomain_E6C43B6CF66A814FE6F7EB761BF5013F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementScenarioAxis_583E7E3205C4873D4827EB761BF560C3" xlink:to="loc_srt_ScenarioUnspecifiedDomain_E6C43B6CF66A814FE6F7EB761BF5013F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_8A224F988FA287721C17EB761BF648D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_ProfitLoss_8A224F988FA287721C17EB761BF648D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_B9BE5C4A292134DAC22BEB761BF6CECA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesNetOfTax_B9BE5C4A292134DAC22BEB761BF6CECA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_4CFA65653627C2F89BE4EB761BF72CCF" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTransactionAndTranslationAdjustmentNetOfTax_4CFA65653627C2F89BE4EB761BF72CCF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_E8BD85A23CDB6D700C3BEB761BF71352" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansAdjustmentNetOfTax_E8BD85A23CDB6D700C3BEB761BF71352" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_950E0EF2B66FF7A8E260EB761BF7A8D0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTaxPeriodIncreaseDecreaseAbstract_3C644844284B5187579AEB761BF6AC60" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_950E0EF2B66FF7A8E260EB761BF7A8D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ComprehensiveIncomeNetOfTax" xlink:label="loc_us-gaap_ComprehensiveIncomeNetOfTax_F56EE472CDDB2D540CF2EB761BF7FADB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_ComprehensiveIncomeNetOfTax_F56EE472CDDB2D540CF2EB761BF7FADB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax_B2B67B9F3613AC3486C9EB761BF7ED47" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossDerivativesQualifyingAsHedgesTax_B2B67B9F3613AC3486C9EB761BF7ED47" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_CC12259B26F53C7CAE18EB761BF8E371" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossForeignCurrencyTranslationAdjustmentTax_CC12259B26F53C7CAE18EB761BF8E371" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_1FC9820F7EA59EAF885DEB761BF8FD27" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_99148F3D6BC014FF035BEB761BF5EC87" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossPensionAndOtherPostretirementBenefitPlansTax_1FC9820F7EA59EAF885DEB761BF8FD27" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsOfIncome" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_11329896D7B2BB813430F3F2569790A9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_StatementTable_11329896D7B2BB813430F3F2569790A9" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_BCECA08A9BBC64CB8D5BF3F25697DA2E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_11329896D7B2BB813430F3F2569790A9" xlink:to="loc_srt_ProductOrServiceAxis_BCECA08A9BBC64CB8D5BF3F25697DA2E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_BDB7F70860C8FF8C32A4F3F25698A6C0_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_BCECA08A9BBC64CB8D5BF3F25697DA2E" xlink:to="loc_srt_ProductsAndServicesDomain_BDB7F70860C8FF8C32A4F3F25698A6C0_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_BDB7F70860C8FF8C32A4F3F25698A6C0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_BCECA08A9BBC64CB8D5BF3F25697DA2E" xlink:to="loc_srt_ProductsAndServicesDomain_BDB7F70860C8FF8C32A4F3F25698A6C0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenuesAbstract" xlink:label="loc_us-gaap_RevenuesAbstract_4DE33385858F2ADE607FF3F25698E4D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_RevenuesAbstract_4DE33385858F2ADE607FF3F25698E4D4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_00A81676D33E414BFD7CF3F2569929C2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_4DE33385858F2ADE607FF3F25698E4D4" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_00A81676D33E414BFD7CF3F2569929C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfRevenue" xlink:label="loc_us-gaap_CostOfRevenue_54C2E1F91D184FB7F372F3F25699B378" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_4DE33385858F2ADE607FF3F25698E4D4" xlink:to="loc_us-gaap_CostOfRevenue_54C2E1F91D184FB7F372F3F25699B378" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GrossProfit" xlink:label="loc_us-gaap_GrossProfit_36F95904E19E48DEE805F3F256995E1F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenuesAbstract_4DE33385858F2ADE607FF3F25698E4D4" xlink:to="loc_us-gaap_GrossProfit_36F95904E19E48DEE805F3F256995E1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingExpensesAbstract" xlink:label="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_SellingGeneralAndAdministrativeExpense_3AD818CDD9A15CBA227AF3F256993627" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_us-gaap_SellingGeneralAndAdministrativeExpense_3AD818CDD9A15CBA227AF3F256993627" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_F3D82AB52A0461EC9C12F3F2569ACADE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_F3D82AB52A0461EC9C12F3F2569ACADE" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Restructuringandstrategictransaction" xlink:label="loc_icui_Restructuringandstrategictransaction_955B6D23B0EED90EEFACF3F2569A9C4B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_icui_Restructuringandstrategictransaction_955B6D23B0EED90EEFACF3F2569A9C4B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_559819D39D0E071866B8F3F2569AB3B7" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationArrangementsChangeInAmountOfContingentConsiderationLiability1_559819D39D0E071866B8F3F2569AB3B7" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Contractsettlement" xlink:label="loc_icui_Contractsettlement_89BFCB01144C42144830F3F2569AA15C" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_icui_Contractsettlement_89BFCB01144C42144830F3F2569AA15C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingExpenses" xlink:label="loc_us-gaap_OperatingExpenses_974508D1CAF83C78BF5FF3F2569A0250" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingExpensesAbstract_DE47EDA4DA6DD385E02DF3F25699BF11" xlink:to="loc_us-gaap_OperatingExpenses_974508D1CAF83C78BF5FF3F2569A0250" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_61A2C43170AED8B02262F3F2569AAD08" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_OperatingIncomeLoss_61A2C43170AED8B02262F3F2569AAD08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestExpense" xlink:label="loc_us-gaap_InterestExpense_21F8BED689A3A2B73D93F3F2569BA0D2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_InterestExpense_21F8BED689A3A2B73D93F3F2569BA0D2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="loc_us-gaap_NonoperatingIncomeExpense_C9AC7E29D15508F48CD7F3F2569B1164" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_NonoperatingIncomeExpense_C9AC7E29D15508F48CD7F3F2569B1164" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_C9463588298AAD742FE1F3F2569B7614" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesMinorityInterestAndIncomeLossFromEquityMethodInvestments_C9463588298AAD742FE1F3F2569B7614" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_IncomeTaxExpenseBenefit_09336F7E7F8288CFC96CF3F2569B7DEE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_IncomeTaxExpenseBenefit_09336F7E7F8288CFC96CF3F2569B7DEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_01617C918D1B6AEB2801F3F2569B8591" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_ProfitLoss_01617C918D1B6AEB2801F3F2569B8591" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareAbstract" xlink:label="loc_us-gaap_EarningsPerShareAbstract_B7F22479FB2BD71842C2F3F2569B77D9" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_EarningsPerShareAbstract_B7F22479FB2BD71842C2F3F2569B77D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_857A3BEF35EE77FC95D2F3F2569CB31D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_B7F22479FB2BD71842C2F3F2569B77D9" xlink:to="loc_us-gaap_EarningsPerShareBasic_857A3BEF35EE77FC95D2F3F2569CB31D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_FC89A9FF2876C4EE46CBF3F2569CAAD0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EarningsPerShareAbstract_B7F22479FB2BD71842C2F3F2569B77D9" xlink:to="loc_us-gaap_EarningsPerShareDiluted_FC89A9FF2876C4EE46CBF3F2569CAAD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_155BCCB8E273574618ABF3F2569C0830" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_77ECDD11B293A527AE82F3F25698CE88" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_155BCCB8E273574618ABF3F2569C0830" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_42306B80D859A2709BE6F3F2569C8055" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_155BCCB8E273574618ABF3F2569C0830" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_42306B80D859A2709BE6F3F2569C8055" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_D430E9ADF1D876F8A0ACF3F2569D6013" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingAbstract_155BCCB8E273574618ABF3F2569C0830" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_D430E9ADF1D876F8A0ACF3F2569D6013" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/CondensedConsolidatedStatementsOfStockholdersEquityStatement" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_CA84EFDB361396B4BCA6ACAC9E72830B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_StatementTable_CA84EFDB361396B4BCA6ACAC9E72830B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_B2130D32823D2625AAE1ACAC9E72E9A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_CA84EFDB361396B4BCA6ACAC9E72830B" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_B2130D32823D2625AAE1ACAC9E72E9A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_B2130D32823D2625AAE1ACAC9E72E9A2" xlink:to="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_B2130D32823D2625AAE1ACAC9E72E9A2" xlink:to="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_CommonStockSharesMember" xlink:label="loc_icui_CommonStockSharesMember_30925CE62F03872CD9AAACAC9E735E95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_icui_CommonStockSharesMember_30925CE62F03872CD9AAACAC9E735E95" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_38E05AF079862F6BA302ACAC9E7352AB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_us-gaap_CommonStockMember_38E05AF079862F6BA302ACAC9E7352AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_099246AC7E49735F65A8ACAC9E740222" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_099246AC7E49735F65A8ACAC9E740222" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="loc_us-gaap_TreasuryStockMember_22526CCD4750913D4DD4ACAC9E74E22D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_us-gaap_TreasuryStockMember_22526CCD4750913D4DD4ACAC9E74E22D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_B88A41BA1976C9B60200ACAC9E7435C8" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_us-gaap_RetainedEarningsMember_B88A41BA1976C9B60200ACAC9E7435C8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_0A3B8FB09FF07A7F7394ACAC9E747E45" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_E4F831F6B2A1C838F1ACACAC9E73E2D5" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_0A3B8FB09FF07A7F7394ACAC9E747E45" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_37A3B51FDFB0B846D74CACAC9E7509DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_37A3B51FDFB0B846D74CACAC9E7509DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="loc_us-gaap_CommonStockSharesOutstanding_CE65597570FCF19613BAACAC9E757E4A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_CommonStockSharesOutstanding_CE65597570FCF19613BAACAC9E757E4A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="loc_us-gaap_StockholdersEquity_9DC85A1323B998B942E9ACAC9E759389" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_StockholdersEquity_9DC85A1323B998B942E9ACAC9E759389" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_614B8DFC9FDA57396708ACAC9E75F148" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesNewIssues_614B8DFC9FDA57396708ACAC9E75F148" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_DE920B349D8D9824E8D6ACAC9E769B56" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueNewIssues_DE920B349D8D9824E8D6ACAC9E769B56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalOther" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_CB306C96A24AB973661EACAC9E766DDC" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalOther_CB306C96A24AB973661EACAC9E766DDC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_FB5DC552BFC76069708AACAC9E766A84" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_SharesPaidForTaxWithholdingForShareBasedCompensation_FB5DC552BFC76069708AACAC9E766A84" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation" xlink:label="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_B77A97BF648142A12C44ACAC9E7683B6" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_AdjustmentsRelatedToTaxWithholdingForShareBasedCompensation_B77A97BF648142A12C44ACAC9E7683B6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7370181B3A5712A4BEB5ACAC9E7669BA" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_7370181B3A5712A4BEB5ACAC9E7669BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_6C3C4B4D83B440A5D0AFACAC9E77992B" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_OtherComprehensiveIncomeForeignCurrencyTransactionAndTranslationGainLossArisingDuringPeriodNetOfTax_6C3C4B4D83B440A5D0AFACAC9E77992B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_5A0D3EF62316C73520B6ACAC9E776C74" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_6F0B04A66FF99A4EC8AFACAC9E74D338" xlink:to="loc_us-gaap_NetIncomeLoss_5A0D3EF62316C73520B6ACAC9E776C74" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DeiDocument" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesAmountsAffectingConsolidatedStatementsOfIncomeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossLineItems" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_C0354D142D3F67EAF0A2F3F257CF6A13" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_C0354D142D3F67EAF0A2F3F257CF6A13" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_B85A4886D2ACB31C76D5F3F257CC4419" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_B85A4886D2ACB31C76D5F3F257CC4419" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4287CB09EE341D87D9B1F3F257CDC4C2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_B85A4886D2ACB31C76D5F3F257CC4419" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4287CB09EE341D87D9B1F3F257CDC4C2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_4287CB09EE341D87D9B1F3F257CDC4C2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_B85A4886D2ACB31C76D5F3F257CC4419" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_4287CB09EE341D87D9B1F3F257CDC4C2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_29F2E913B2D6AA1C613BF3F257CD9CE7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_29F2E913B2D6AA1C613BF3F257CD9CE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_FFBFCB67CAD208E8F2DEF3F257CD429F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_29F2E913B2D6AA1C613BF3F257CD9CE7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_FFBFCB67CAD208E8F2DEF3F257CD429F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_FFBFCB67CAD208E8F2DEF3F257CD429F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_29F2E913B2D6AA1C613BF3F257CD9CE7" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_FFBFCB67CAD208E8F2DEF3F257CD429F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_CAC382B4CF98FEA482DAF3F257CD5651" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_CAC382B4CF98FEA482DAF3F257CD5651" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_45B17BB06D25E0860EA7F3F257CEF45F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_CAC382B4CF98FEA482DAF3F257CD5651" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_45B17BB06D25E0860EA7F3F257CEF45F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_45B17BB06D25E0860EA7F3F257CEF45F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_CAC382B4CF98FEA482DAF3F257CD5651" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_45B17BB06D25E0860EA7F3F257CEF45F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_1B53F1A43B036E49F3F4F3F257CEDF24" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:to="loc_us-gaap_HedgingDesignationAxis_1B53F1A43B036E49F3F4F3F257CEDF24" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_8EE1F44E2C99778D793BF3F257CE33AB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_1B53F1A43B036E49F3F4F3F257CEDF24" xlink:to="loc_us-gaap_HedgingDesignationDomain_8EE1F44E2C99778D793BF3F257CE33AB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_8EE1F44E2C99778D793BF3F257CE33AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_1B53F1A43B036E49F3F4F3F257CEDF24" xlink:to="loc_us-gaap_HedgingDesignationDomain_8EE1F44E2C99778D793BF3F257CE33AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C09ACC45CC738CDF5CF6F3F257CEC704" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipByIncomeStatementLocationByDerivativeInstrumentRiskTable_BC601E32C19EF009CC2CF3F257CC97C7" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C09ACC45CC738CDF5CF6F3F257CEC704" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_2182DB5E7C5C926B961CF3F257CF495A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C09ACC45CC738CDF5CF6F3F257CEC704" xlink:to="loc_us-gaap_HedgingRelationshipDomain_2182DB5E7C5C926B961CF3F257CF495A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_2182DB5E7C5C926B961CF3F257CF495A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_C09ACC45CC738CDF5CF6F3F257CEC704" xlink:to="loc_us-gaap_HedgingRelationshipDomain_2182DB5E7C5C926B961CF3F257CF495A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeGainLossOnDerivativeNet" xlink:label="loc_us-gaap_DerivativeGainLossOnDerivativeNet_BD12268D627957FDF9AEF3F257CFFA72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossLineItems_C0354D142D3F67EAF0A2F3F257CF6A13" xlink:to="loc_us-gaap_DerivativeGainLossOnDerivativeNet_BD12268D627957FDF9AEF3F257CFFA72" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesCashFlowHedgeActivityIncludedInAccumulatedOtherComprehensiveIncomeLossDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90C0362E8F602FCD03B065630FE25ACE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable" xlink:label="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90C0362E8F602FCD03B065630FE25ACE" xlink:to="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_B00080E937BF45E2E42465630FDEB071" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_B00080E937BF45E2E42465630FDEB071" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ABCCD57366812A74A64765630FDE59C4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_B00080E937BF45E2E42465630FDEB071" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ABCCD57366812A74A64765630FDE59C4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_ABCCD57366812A74A64765630FDE59C4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_B00080E937BF45E2E42465630FDEB071" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_ABCCD57366812A74A64765630FDE59C4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="loc_us-gaap_CostOfSalesMember_C8FAA91B2C3149C1E94065630FDF8F9B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementLocationDomain_ABCCD57366812A74A64765630FDE59C4" xlink:to="loc_us-gaap_CostOfSalesMember_C8FAA91B2C3149C1E94065630FDF8F9B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_CE3FA9F7E25D914DEDCD65630FDF4685" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_CE3FA9F7E25D914DEDCD65630FDF4685" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_DBA2104E0218E7B7E47065630FDF3D57_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CE3FA9F7E25D914DEDCD65630FDF4685" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_DBA2104E0218E7B7E47065630FDF3D57_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_DBA2104E0218E7B7E47065630FDF3D57" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_CE3FA9F7E25D914DEDCD65630FDF4685" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_DBA2104E0218E7B7E47065630FDF3D57" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_3802175B21C59A59B33B65630FE0B38A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_DBA2104E0218E7B7E47065630FDF3D57" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_3802175B21C59A59B33B65630FE0B38A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_DF6B2CF5C2E84ED0D4FC65630FE02346" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:to="loc_us-gaap_HedgingDesignationAxis_DF6B2CF5C2E84ED0D4FC65630FE02346" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_086EA2960D46B5DD4FA665630FE15E46_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_DF6B2CF5C2E84ED0D4FC65630FE02346" xlink:to="loc_us-gaap_HedgingDesignationDomain_086EA2960D46B5DD4FA665630FE15E46_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_086EA2960D46B5DD4FA665630FE15E46" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_DF6B2CF5C2E84ED0D4FC65630FE02346" xlink:to="loc_us-gaap_HedgingDesignationDomain_086EA2960D46B5DD4FA665630FE15E46" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis" xlink:label="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_67DB4A9510B35041671F65630FE1D328" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresTable_21462330313A625976EA65630FDE5186" xlink:to="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_67DB4A9510B35041671F65630FE1D328" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_E947B9220CCF2CD9139965630FE1EEE6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_67DB4A9510B35041671F65630FE1D328" xlink:to="loc_us-gaap_HedgingRelationshipDomain_E947B9220CCF2CD9139965630FE1EEE6_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingRelationshipDomain" xlink:label="loc_us-gaap_HedgingRelationshipDomain_E947B9220CCF2CD9139965630FE1EEE6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentsGainLossByHedgingRelationshipAxis_67DB4A9510B35041671F65630FE1D328" xlink:to="loc_us-gaap_HedgingRelationshipDomain_E947B9220CCF2CD9139965630FE1EEE6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CashFlowHedgingMember" xlink:label="loc_us-gaap_CashFlowHedgingMember_C92816FA69553941857F65630FE19FB2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingRelationshipDomain_E947B9220CCF2CD9139965630FE1EEE6" xlink:to="loc_us-gaap_CashFlowHedgingMember_C92816FA69553941857F65630FE19FB2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax_2C329A67BDBF593848B165630FE2FE3D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90C0362E8F602FCD03B065630FE25ACE" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodBeforeTax_2C329A67BDBF593848B165630FE2FE3D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion" xlink:label="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_F0F837DFB28AB25C80FB65630FE282D6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeInstrumentsAndHedgingActivitiesDisclosuresLineItems_90C0362E8F602FCD03B065630FE25ACE" xlink:to="loc_us-gaap_DerivativeInstrumentsGainReclassifiedFromAccumulatedOCIIntoIncomeEffectivePortion_F0F837DFB28AB25C80FB65630FE282D6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDerivativeInstrumentsAndHedgingActivitiesFvOfDerivativeInstrumentsIncludedWithinConsolidatedBalanceSheetDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativesFairValueLineItems" xlink:label="loc_us-gaap_DerivativesFairValueLineItems_ADD5105FA00DE7A4F088AC990C2AF407" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable" xlink:label="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ADD5105FA00DE7A4F088AC990C2AF407" xlink:to="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_C480E4629A3C40A58753AC990C267076" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_C480E4629A3C40A58753AC990C267076" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_39C117B1E0696EDC0E4CAC990C26F583_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_C480E4629A3C40A58753AC990C267076" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_39C117B1E0696EDC0E4CAC990C26F583_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_39C117B1E0696EDC0E4CAC990C26F583" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_C480E4629A3C40A58753AC990C267076" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_39C117B1E0696EDC0E4CAC990C26F583" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignExchangeForwardMember" xlink:label="loc_us-gaap_ForeignExchangeForwardMember_243BC4E1122DC8C22FBDAC990C27F557" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_39C117B1E0696EDC0E4CAC990C26F583" xlink:to="loc_us-gaap_ForeignExchangeForwardMember_243BC4E1122DC8C22FBDAC990C27F557" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationAxis" xlink:label="loc_us-gaap_HedgingDesignationAxis_05A5801B276A98AE1E8AAC990C2734A9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:to="loc_us-gaap_HedgingDesignationAxis_05A5801B276A98AE1E8AAC990C2734A9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_356BB666C12BD2809B77AC990C27B550_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_HedgingDesignationAxis_05A5801B276A98AE1E8AAC990C2734A9" xlink:to="loc_us-gaap_HedgingDesignationDomain_356BB666C12BD2809B77AC990C27B550_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_HedgingDesignationDomain" xlink:label="loc_us-gaap_HedgingDesignationDomain_356BB666C12BD2809B77AC990C27B550" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_HedgingDesignationAxis_05A5801B276A98AE1E8AAC990C2734A9" xlink:to="loc_us-gaap_HedgingDesignationDomain_356BB666C12BD2809B77AC990C27B550" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DesignatedAsHedgingInstrumentMember" xlink:label="loc_us-gaap_DesignatedAsHedgingInstrumentMember_B2E001A05FB0AAFAE509AC990C274E18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HedgingDesignationDomain_356BB666C12BD2809B77AC990C27B550" xlink:to="loc_us-gaap_DesignatedAsHedgingInstrumentMember_B2E001A05FB0AAFAE509AC990C274E18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_CCDC970BC71F5A5390B8AC990C285535" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_CCDC970BC71F5A5390B8AC990C285535" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CCDC970BC71F5A5390B8AC990C285535" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_CCDC970BC71F5A5390B8AC990C285535" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_8E5E7A029FD5DB28D8F1AC990C28C4A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_8E5E7A029FD5DB28D8F1AC990C28C4A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsAssetsMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_840A800665DECB655BA0AC990C292DE7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsAssetsMember_840A800665DECB655BA0AC990C292DE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember" xlink:label="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_2674257CC0386804ACF6AC990C298F2C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:to="loc_us-gaap_DerivativeFinancialInstrumentsLiabilitiesMember_2674257CC0386804ACF6AC990C298F2C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_B093F5D6B2763ED49C0AAC990C29EA48" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_B093F5D6B2763ED49C0AAC990C29EA48" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_51F2DA8D6863EB42C90EAC990C2974E1" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_D31DB543F9973EB4C0AEAC990C280B99" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_51F2DA8D6863EB42C90EAC990C2974E1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionAxis" xlink:label="loc_us-gaap_PositionAxis_D5708348E7F32B0A34EBAC990C290428" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValuesDerivativesBalanceSheetLocationByDerivativeContractTypeByHedgingDesignationTable_5DFDE8A148FF33F5EB3CAC990C26078B" xlink:to="loc_us-gaap_PositionAxis_D5708348E7F32B0A34EBAC990C290428" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionDomain" xlink:label="loc_us-gaap_PositionDomain_DFECDC2F811123306BE0AC990C2A565D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_D5708348E7F32B0A34EBAC990C290428" xlink:to="loc_us-gaap_PositionDomain_DFECDC2F811123306BE0AC990C2A565D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionDomain" xlink:label="loc_us-gaap_PositionDomain_DFECDC2F811123306BE0AC990C2A565D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_D5708348E7F32B0A34EBAC990C290428" xlink:to="loc_us-gaap_PositionDomain_DFECDC2F811123306BE0AC990C2A565D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssets" xlink:label="loc_us-gaap_DerivativeAssets_C9C2E37736A90A636054AC990C2A4F5B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ADD5105FA00DE7A4F088AC990C2AF407" xlink:to="loc_us-gaap_DerivativeAssets_C9C2E37736A90A636054AC990C2A4F5B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLiabilities" xlink:label="loc_us-gaap_DerivativeLiabilities_CF1585827DAFE901BCFEAC990C2A35DB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativesFairValueLineItems_ADD5105FA00DE7A4F088AC990C2AF407" xlink:to="loc_us-gaap_DerivativeLiabilities_CF1585827DAFE901BCFEAC990C2A35DB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLineItems" xlink:label="loc_us-gaap_DerivativeLineItems_AF72C60C7571716F6593ACAC9CABE583" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeTable" xlink:label="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_AF72C60C7571716F6593ACAC9CABE583" xlink:to="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_EnergyAxis" xlink:label="loc_srt_EnergyAxis_33CC28E059F1B1ABC191ACAC9CABE718" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:to="loc_srt_EnergyAxis_33CC28E059F1B1ABC191ACAC9CABE718" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_EnergyDomain" xlink:label="loc_srt_EnergyDomain_586D084EFC979DB3D0ECACAC9CABD942_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_EnergyAxis_33CC28E059F1B1ABC191ACAC9CABE718" xlink:to="loc_srt_EnergyDomain_586D084EFC979DB3D0ECACAC9CABD942_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_EnergyDomain" xlink:label="loc_srt_EnergyDomain_586D084EFC979DB3D0ECACAC9CABD942" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_EnergyAxis_33CC28E059F1B1ABC191ACAC9CABE718" xlink:to="loc_srt_EnergyDomain_586D084EFC979DB3D0ECACAC9CABD942" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_95848EB902A19B5D6918ACAC9CAB579F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:to="loc_us-gaap_VariableRateAxis_95848EB902A19B5D6918ACAC9CAB579F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_DD95314B1F9A65395D6BACAC9CABB763_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_95848EB902A19B5D6918ACAC9CAB579F" xlink:to="loc_us-gaap_VariableRateDomain_DD95314B1F9A65395D6BACAC9CABB763_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_DD95314B1F9A65395D6BACAC9CABB763" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_95848EB902A19B5D6918ACAC9CAB579F" xlink:to="loc_us-gaap_VariableRateDomain_DD95314B1F9A65395D6BACAC9CABB763" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_FEB8219B6F4A5837E08BACAC9CAB1CEC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_FEB8219B6F4A5837E08BACAC9CAB1CEC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_FEB8219B6F4A5837E08BACAC9CAB1CEC" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_FEB8219B6F4A5837E08BACAC9CAB1CEC" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Hedge2Member" xlink:label="loc_icui_Hedge2Member_6734678E35C168F58C73ACAC9CAB72FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55" xlink:to="loc_icui_Hedge2Member_6734678E35C168F58C73ACAC9CAB72FF" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Hedge3MemberMember" xlink:label="loc_icui_Hedge3MemberMember_2F761000A0A28EDBCEC8ACAC9CABF544" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_B5E6A2F1CC98EFBB18FCACAC9CAB3E55" xlink:to="loc_icui_Hedge3MemberMember_2F761000A0A28EDBCEC8ACAC9CABF544" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionAxis" xlink:label="loc_us-gaap_PositionAxis_926645E904D58E73AF7DACAC9CAB4D6F" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:to="loc_us-gaap_PositionAxis_926645E904D58E73AF7DACAC9CAB4D6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionDomain" xlink:label="loc_us-gaap_PositionDomain_F5F6D5A253F5A81B39CEACAC9CABDC08_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PositionAxis_926645E904D58E73AF7DACAC9CAB4D6F" xlink:to="loc_us-gaap_PositionDomain_F5F6D5A253F5A81B39CEACAC9CABDC08_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PositionDomain" xlink:label="loc_us-gaap_PositionDomain_F5F6D5A253F5A81B39CEACAC9CABDC08" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PositionAxis_926645E904D58E73AF7DACAC9CAB4D6F" xlink:to="loc_us-gaap_PositionDomain_F5F6D5A253F5A81B39CEACAC9CABDC08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_E9FCAB581F9FAE7B8419ACAC9CABE029" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D71D46FA8E2ED23C29F6ACAC9CAB64F7" xlink:to="loc_srt_RangeAxis_E9FCAB581F9FAE7B8419ACAC9CABE029" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_429D771D9AA96591A7DDACAC9CABDEF4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_E9FCAB581F9FAE7B8419ACAC9CABE029" xlink:to="loc_srt_RangeMember_429D771D9AA96591A7DDACAC9CABDEF4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_429D771D9AA96591A7DDACAC9CABDEF4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_E9FCAB581F9FAE7B8419ACAC9CABE029" xlink:to="loc_srt_RangeMember_429D771D9AA96591A7DDACAC9CABDEF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months" xlink:label="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_26F3B2109F9F800C50AAACAC9CAB88E7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_AF72C60C7571716F6593ACAC9CABE583" xlink:to="loc_us-gaap_ForeignCurrencyCashFlowHedgeGainLossToBeReclassifiedDuringNext12Months_26F3B2109F9F800C50AAACAC9CAB88E7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeForwardExchangeRate1" xlink:label="loc_us-gaap_DerivativeForwardExchangeRate1_89E25A40CDA64D262945ACAC9CAB2A2B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_AF72C60C7571716F6593ACAC9CABE583" xlink:to="loc_us-gaap_DerivativeForwardExchangeRate1_89E25A40CDA64D262945ACAC9CAB2A2B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssetNotionalAmount" xlink:label="loc_us-gaap_DerivativeAssetNotionalAmount_F6D02EBC69FB303BF42CACAC9CBA5B2A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_AF72C60C7571716F6593ACAC9CABE583" xlink:to="loc_us-gaap_DerivativeAssetNotionalAmount_F6D02EBC69FB303BF42CACAC9CBA5B2A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/DerivativeFinancialInstrumentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurement" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationHospiraDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_5A4F46CA6A98FB151506C6AB0FF49158" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_5A4F46CA6A98FB151506C6AB0FF49158" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_81994E02E2996406A025C6E56FCC244B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_5A4F46CA6A98FB151506C6AB0FF49158" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_81994E02E2996406A025C6E56FCC244B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74472B519C999E7A5A91C6E57243EA71_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_81994E02E2996406A025C6E56FCC244B" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74472B519C999E7A5A91C6E57243EA71_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74472B519C999E7A5A91C6E57243EA71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_81994E02E2996406A025C6E56FCC244B" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74472B519C999E7A5A91C6E57243EA71" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_HospiraMember" xlink:label="loc_icui_HospiraMember_2EE3141DE914A8766ABDC6E56FE46FF3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_74472B519C999E7A5A91C6E57243EA71" xlink:to="loc_icui_HospiraMember_2EE3141DE914A8766ABDC6E56FE46FF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_D69BABAE74B2F8E22C5DC6AB0FF8AC25" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_5A4F46CA6A98FB151506C6AB0FF49158" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_D69BABAE74B2F8E22C5DC6AB0FF8AC25" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_D69BABAE74B2F8E22C5DC6AB0FF8AC25" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_D69BABAE74B2F8E22C5DC6AB0FF8AC25" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_MeasurementInputCostofDebtDomain" xlink:label="loc_icui_MeasurementInputCostofDebtDomain_87B9AA176F4FE7B2DEDFC6E56FF85A72" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE" xlink:to="loc_icui_MeasurementInputCostofDebtDomain_87B9AA176F4FE7B2DEDFC6E56FF85A72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_48A5A1833084BF033454C6E5700CD342" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_CFE0B1F30184B6C06B83C6AB0FF89CCE" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_48A5A1833084BF033454C6E5700CD342" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_FairValueAssumptionsExpectedVolatilityRateAdjustedEBITDA" xlink:label="loc_icui_FairValueAssumptionsExpectedVolatilityRateAdjustedEBITDA_05FBF74E8ABF8A8748C7C6E56F752ABB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:to="loc_icui_FairValueAssumptionsExpectedVolatilityRateAdjustedEBITDA_05FBF74E8ABF8A8748C7C6E56F752ABB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_EA4BDCFE7A9D6AE7AE72C6E56F93E96A" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_EA4BDCFE7A9D6AE7AE72C6E56F93E96A" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_FairValueAssumptionsMarketPriceofRisk" xlink:label="loc_icui_FairValueAssumptionsMarketPriceofRisk_A1045261486C6331DA6BC6E56FA6259B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:to="loc_icui_FairValueAssumptionsMarketPriceofRisk_A1045261486C6331DA6BC6E56FA6259B" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_FairValueAssumptionsCostofDebt" xlink:label="loc_icui_FairValueAssumptionsCostofDebt_6C46EA0A99A3084AB5ECC6E56FB856A0" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_00AC0E8DD5A89840610FC6AB0FF992B5" xlink:to="loc_icui_FairValueAssumptionsCostofDebt_6C46EA0A99A3084AB5ECC6E56FB856A0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueInputsLiabilitiesQuantitativeInformationPursuitDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_67A76B78F232F1647F37C6E846261392" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_F7EE4E3F167331CECAE2C6E8460D3A02" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_67A76B78F232F1647F37C6E846261392" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_F7EE4E3F167331CECAE2C6E8460D3A02" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="loc_us-gaap_MeasurementInputTypeAxis_E5F61ABF43FF60D5E11BC6E846245BE5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_F7EE4E3F167331CECAE2C6E8460D3A02" xlink:to="loc_us-gaap_MeasurementInputTypeAxis_E5F61ABF43FF60D5E11BC6E846245BE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_E5F61ABF43FF60D5E11BC6E846245BE5" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_MeasurementInputTypeAxis_E5F61ABF43FF60D5E11BC6E846245BE5" xlink:to="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_MeasurementinputadjustedEBITDAvolatilityDomain" xlink:label="loc_icui_MeasurementinputadjustedEBITDAvolatilityDomain_67181A503B5B43BB7A69C6E84679732B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:to="loc_icui_MeasurementinputadjustedEBITDAvolatilityDomain_67181A503B5B43BB7A69C6E84679732B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputDiscountRateMember" xlink:label="loc_us-gaap_MeasurementInputDiscountRateMember_729578B258CA58560608C6E8468E3840" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:to="loc_us-gaap_MeasurementInputDiscountRateMember_729578B258CA58560608C6E8468E3840" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:label="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_0430B8D62F1DD9BEFE26C6E846A3FA2E" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:to="loc_us-gaap_MeasurementInputRiskFreeInterestRateMember_0430B8D62F1DD9BEFE26C6E846A3FA2E" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_MeasurementInputMarketPriceofRiskDomain" xlink:label="loc_icui_MeasurementInputMarketPriceofRiskDomain_7FCAF7472A7F8F19F2D9C6E846B8A580" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MeasurementInputTypeDomain_C4F466AB2C4E3C2C6AC5C6E84625DB17" xlink:to="loc_icui_MeasurementInputMarketPriceofRiskDomain_7FCAF7472A7F8F19F2D9C6E846B8A580" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput" xlink:label="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_32EA654EBF9FC94C44F7C6E8465ED770" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesLineItems_67A76B78F232F1647F37C6E846261392" xlink:to="loc_us-gaap_BusinessCombinationContingentConsiderationLiabilityMeasurementInput_32EA654EBF9FC94C44F7C6E8465ED770" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4061717C155E639ED1A0C6AB4B0D7D88" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A580B872242586DBE2B9C6AB4B082829" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4061717C155E639ED1A0C6AB4B0D7D88" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A580B872242586DBE2B9C6AB4B082829" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_218B9D6BD7E91180CD39C6AB4B2E204C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_A580B872242586DBE2B9C6AB4B082829" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_218B9D6BD7E91180CD39C6AB4B2E204C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_218B9D6BD7E91180CD39C6AB4B2E204C" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_218B9D6BD7E91180CD39C6AB4B2E204C" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_HospiraMember" xlink:label="loc_icui_HospiraMember_DBB6F0A73A583A81E4DCC6AB4B3B0BAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9" xlink:to="loc_icui_HospiraMember_DBB6F0A73A583A81E4DCC6AB4B3B0BAD" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_PursuitVascularInc.Member" xlink:label="loc_icui_PursuitVascularInc.Member_7BA1DE491B4745E3F483C6AE8C92EA88" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_0517DC2092B8935B38D7C6AB4C3E7FB9" xlink:to="loc_icui_PursuitVascularInc.Member_7BA1DE491B4745E3F483C6AE8C92EA88" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Contingentconsiderationgross" xlink:label="loc_icui_Contingentconsiderationgross_FDD327B9DCE4D7B9C553C6AB4B1F9C22" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_4061717C155E639ED1A0C6AB4B0D7D88" xlink:to="loc_icui_Contingentconsiderationgross_FDD327B9DCE4D7B9C553C6AB4B1F9C22" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementFairValueMeasurementsRecurringBasisDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_CD4E541B9997532745DDC6AB14A1565E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_CD4E541B9997532745DDC6AB14A1565E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByLiabilityClassAxis" xlink:label="loc_us-gaap_FairValueByLiabilityClassAxis_71A803FCAD3DFBD34EFFC6AB14A61F84" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_CD4E541B9997532745DDC6AB14A1565E" xlink:to="loc_us-gaap_FairValueByLiabilityClassAxis_71A803FCAD3DFBD34EFFC6AB14A61F84" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_71A803FCAD3DFBD34EFFC6AB14A61F84" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByLiabilityClassAxis_71A803FCAD3DFBD34EFFC6AB14A61F84" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_EarnoutliabilityMember" xlink:label="loc_icui_EarnoutliabilityMember_47AB64193320D1704488C6AB14A7D173" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA" xlink:to="loc_icui_EarnoutliabilityMember_47AB64193320D1704488C6AB14A7D173" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LiabilitiesTotalMember" xlink:label="loc_us-gaap_LiabilitiesTotalMember_78853560580FBC4129D7C6AB14A8B335" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisUnobservableInputReconciliationByLiabilityClassDomain_443919F3F2AEA5E75EAAC6AB14A71BCA" xlink:to="loc_us-gaap_LiabilitiesTotalMember_78853560580FBC4129D7C6AB14A8B335" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2F279247AAFEBDA0F5B9C6AB14A88BD8" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_CD4E541B9997532745DDC6AB14A1565E" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2F279247AAFEBDA0F5B9C6AB14A88BD8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2F279247AAFEBDA0F5B9C6AB14A88BD8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_2F279247AAFEBDA0F5B9C6AB14A88BD8" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_37E31EA8A203C9EC9151C6AB14A9BFC5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_37E31EA8A203C9EC9151C6AB14A9BFC5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_CFD9583CE4E90C3E9A52C6AB14A9D769" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_CFD9583CE4E90C3E9A52C6AB14A9D769" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_5E50D80D2CED33C87074C6AB14A94D35" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_825B877A870F5A9D8E2AC6AB14A88257" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_5E50D80D2CED33C87074C6AB14A94D35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_0E0CD6FC1889883EDA41C6AB14A92598" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_CD4E541B9997532745DDC6AB14A1565E" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_0E0CD6FC1889883EDA41C6AB14A92598" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_0E0CD6FC1889883EDA41C6AB14A92598" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_0E0CD6FC1889883EDA41C6AB14A92598" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_A3A074658495B2D98651C6AB14AA5D3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_A3A074658495B2D98651C6AB14AA5D3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccruedLiabilitiesMember" xlink:label="loc_us-gaap_AccruedLiabilitiesMember_BB60149DEFDA7553C9B0C6AB14AABC2D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711" xlink:to="loc_us-gaap_AccruedLiabilitiesMember_BB60149DEFDA7553C9B0C6AB14AABC2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherNoncurrentLiabilitiesMember" xlink:label="loc_us-gaap_OtherNoncurrentLiabilitiesMember_EF17FAFD4726C7A0C6F1C6AB14AA64F6" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_25269B0F82308589C367C6AB14A96711" xlink:to="loc_us-gaap_OtherNoncurrentLiabilitiesMember_EF17FAFD4726C7A0C6F1C6AB14AA64F6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue" xlink:label="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_3491160784F5E3FA64C4C6B0E21B38C5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_FairValueMeasurementWithUnobservableInputsReconciliationsRecurringBasisLiabilityValue_3491160784F5E3FA64C4C6B0E21B38C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesCurrent_91E232C2EEEFA0B31152C6AB14AB2AE5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesCurrent_91E232C2EEEFA0B31152C6AB14AB2AE5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_843A3BCDAFD1F4A8BA51C6AB14AB7870" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_AvailableForSaleSecurities_843A3BCDAFD1F4A8BA51C6AB14AB7870" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_B50E08757ECFD0F30521C6AB14ABB6A1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_B50E08757ECFD0F30521C6AB14ABB6A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetsFairValueDisclosure" xlink:label="loc_us-gaap_AssetsFairValueDisclosure_0C7D863F1A50A6529523C6AB14AB1CCD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_AssetsFairValueDisclosure_0C7D863F1A50A6529523C6AB14AB1CCD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NonfinancialLiabilitiesFairValueDisclosure" xlink:label="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_38AAD0AADA8B1AD3B0F7C6AB14AC1046" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_NonfinancialLiabilitiesFairValueDisclosure_38AAD0AADA8B1AD3B0F7C6AB14AC1046" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_8B68977DC985101E7824C6AB14AC36DE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_8B68977DC985101E7824C6AB14AC36DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss" xlink:label="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_E830DF5BAF4A1E2FD6A4C6B0E5A57C39" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_A1C059B8A4542BCA0817C6AB14AA3D85" xlink:to="loc_us-gaap_FairValueLiabilitiesMeasuredOnRecurringBasisChangeInUnrealizedGainLoss_E830DF5BAF4A1E2FD6A4C6B0E5A57C39" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/FairValueMeasurementTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssets5YearAmortizationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssetsGoodwillTableDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_83661616C88BD37CDAF7ACAC9BA162DD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_83661616C88BD37CDAF7ACAC9BA162DD" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_B114A55FB07C25609781ACAC9B9FEDFC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:to="loc_srt_ConsolidationItemsAxis_B114A55FB07C25609781ACAC9B9FEDFC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_8CE12320E98784F3A719ACAC9B9FCF04_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_B114A55FB07C25609781ACAC9B9FEDFC" xlink:to="loc_srt_ConsolidationItemsDomain_8CE12320E98784F3A719ACAC9B9FCF04_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_8CE12320E98784F3A719ACAC9B9FCF04" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_B114A55FB07C25609781ACAC9B9FEDFC" xlink:to="loc_srt_ConsolidationItemsDomain_8CE12320E98784F3A719ACAC9B9FCF04" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_69B5598CF53FDF73EE70ACAC9B9FC71F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_69B5598CF53FDF73EE70ACAC9B9FC71F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_FC030920B94AE26CE3EEACAC9BA015F8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_69B5598CF53FDF73EE70ACAC9B9FC71F" xlink:to="loc_us-gaap_SegmentDomain_FC030920B94AE26CE3EEACAC9BA015F8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_FC030920B94AE26CE3EEACAC9BA015F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_69B5598CF53FDF73EE70ACAC9B9FC71F" xlink:to="loc_us-gaap_SegmentDomain_FC030920B94AE26CE3EEACAC9BA015F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_0C6A2CE43ADC1E6624E3ACAC9BA05D7B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_0C6A2CE43ADC1E6624E3ACAC9BA05D7B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9FF063ACD4BB519EB94DACAC9BA0827F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_0C6A2CE43ADC1E6624E3ACAC9BA05D7B" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9FF063ACD4BB519EB94DACAC9BA0827F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_9FF063ACD4BB519EB94DACAC9BA0827F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_0C6A2CE43ADC1E6624E3ACAC9BA05D7B" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_9FF063ACD4BB519EB94DACAC9BA0827F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_1EC238CCF642753680EDACAC9BA0D221" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_69D663C415FEA7A9602BACAC9B9E1B45" xlink:to="loc_srt_RangeAxis_1EC238CCF642753680EDACAC9BA0D221" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_8D528F1DCADBCE717E8FACAC9BA09A54_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_1EC238CCF642753680EDACAC9BA0D221" xlink:to="loc_srt_RangeMember_8D528F1DCADBCE717E8FACAC9BA09A54_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_8D528F1DCADBCE717E8FACAC9BA09A54" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_1EC238CCF642753680EDACAC9BA0D221" xlink:to="loc_srt_RangeMember_8D528F1DCADBCE717E8FACAC9BA09A54" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_D79CA92158788A1D3F74ACAC9BA14D18" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_83661616C88BD37CDAF7ACAC9BA162DD" xlink:to="loc_us-gaap_Goodwill_D79CA92158788A1D3F74ACAC9BA14D18" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillForeignCurrencyTranslationGainLoss" xlink:label="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_654171EC6358901F1BB9ACAC9BA188EB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_83661616C88BD37CDAF7ACAC9BA162DD" xlink:to="loc_us-gaap_GoodwillForeignCurrencyTranslationGainLoss_654171EC6358901F1BB9ACAC9BA188EB" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssetsIntangiblesTableDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsLineItems" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable" xlink:label="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_2667B2948276EDB27E4D65243108D704" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_2667B2948276EDB27E4D65243108D704" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_2667B2948276EDB27E4D65243108D704" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_2667B2948276EDB27E4D65243108D704" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PatentsMember" xlink:label="loc_us-gaap_PatentsMember_2804C523BB62D4F00AA765243108DE6B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_PatentsMember_2804C523BB62D4F00AA765243108DE6B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerContractsMember" xlink:label="loc_us-gaap_CustomerContractsMember_837477CF1D0C8033795B652431098D63" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_CustomerContractsMember_837477CF1D0C8033795B652431098D63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelatedIntangibleAssetsMember" xlink:label="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_F2B7DA4F951615B3D3E665243109B470" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_CustomerRelatedIntangibleAssetsMember_F2B7DA4F951615B3D3E665243109B470" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TrademarksMember" xlink:label="loc_us-gaap_TrademarksMember_3CD5F4956686649C88C665243109A7DE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_TrademarksMember_3CD5F4956686649C88C665243109A7DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TradeNamesMember" xlink:label="loc_us-gaap_TradeNamesMember_B12DEAB3929C1B4CE216652431092A94" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_TradeNamesMember_B12DEAB3929C1B4CE216652431092A94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DevelopedTechnologyRightsMember" xlink:label="loc_us-gaap_DevelopedTechnologyRightsMember_22B477696045BAB8071C6524310A7987" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_DevelopedTechnologyRightsMember_22B477696045BAB8071C6524310A7987" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_NoncompeteAgreementsMember" xlink:label="loc_us-gaap_NoncompeteAgreementsMember_15926A58F9AF765705706529977D7CCB" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_3CDAF056FCEB623F5273652431087A92" xlink:to="loc_us-gaap_NoncompeteAgreementsMember_15926A58F9AF765705706529977D7CCB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_26974F8AAF20CC90508B6524310AB845" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:to="loc_srt_ConsolidationItemsAxis_26974F8AAF20CC90508B6524310AB845" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_16558FA3F189D0800CB26524310A301B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_26974F8AAF20CC90508B6524310AB845" xlink:to="loc_srt_ConsolidationItemsDomain_16558FA3F189D0800CB26524310A301B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_16558FA3F189D0800CB26524310A301B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_26974F8AAF20CC90508B6524310AB845" xlink:to="loc_srt_ConsolidationItemsDomain_16558FA3F189D0800CB26524310A301B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_E6AD648CFF70CA4E54D96524310A7BAA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_E6AD648CFF70CA4E54D96524310A7BAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_AD0F878F922FDDA95F3A6524310B3499_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E6AD648CFF70CA4E54D96524310A7BAA" xlink:to="loc_us-gaap_SegmentDomain_AD0F878F922FDDA95F3A6524310B3499_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_AD0F878F922FDDA95F3A6524310B3499" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E6AD648CFF70CA4E54D96524310A7BAA" xlink:to="loc_us-gaap_SegmentDomain_AD0F878F922FDDA95F3A6524310B3499" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_7C798F45AE9E7C7C9C736524310BCAB5" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfFiniteLivedIntangibleAssetsTable_18329CF6B8E334AF197665243107AB80" xlink:to="loc_srt_RangeAxis_7C798F45AE9E7C7C9C736524310BCAB5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D70C627FC75DC62573166524310B2482_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_7C798F45AE9E7C7C9C736524310BCAB5" xlink:to="loc_srt_RangeMember_D70C627FC75DC62573166524310B2482_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_D70C627FC75DC62573166524310B2482" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_7C798F45AE9E7C7C9C736524310BCAB5" xlink:to="loc_srt_RangeMember_D70C627FC75DC62573166524310B2482" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_4EEE0C841671E9036FDA6524310C951C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_4EEE0C841671E9036FDA6524310C951C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_4E965A36CE6B3470CB136524310CFC67" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_4E965A36CE6B3470CB136524310CFC67" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_03193C982758B9A12D306524310DCBA4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_03193C982758B9A12D306524310DCBA4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_84D4C8C89CF35899D79E6524310D5DA1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_84D4C8C89CF35899D79E6524310D5DA1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_F111A05F3E6C5DC1317B6524310DC342" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_F111A05F3E6C5DC1317B6524310DC342" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_803EB81A4DCA69ACE3F96524310D2948" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_803EB81A4DCA69ACE3F96524310D2948" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_132A86FC5F95E3E7B0906524310E3336" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsLineItems_C652065BCBE80D3F08106524310BF7CB" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_132A86FC5F95E3E7B0906524310E3336" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssetsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/GoodwillAndIntangibleAssetsTextDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/IncomeTaxesEffectiveTaxRateDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/Inventories" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/InventoriesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/InventoriesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/InvestmentSecuritiesDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_D12219F185DBAE854FA8F3F2598280F7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_C78A1EA49D4A0A78B18FF3F2598281FF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_D12219F185DBAE854FA8F3F2598280F7" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_C78A1EA49D4A0A78B18FF3F2598281FF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_CC34E711673A7372BF04F3F259827921" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_C78A1EA49D4A0A78B18FF3F2598281FF" xlink:to="loc_srt_RangeAxis_CC34E711673A7372BF04F3F259827921" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_CC34E711673A7372BF04F3F259827921" xlink:to="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_CC34E711673A7372BF04F3F259827921" xlink:to="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_87F9F2AC3FA9BF70C3E4F3F259822AC2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803" xlink:to="loc_srt_MinimumMember_87F9F2AC3FA9BF70C3E4F3F259822AC2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_F27900E2262F251326BBF3F25982E4D4" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_A74D32D996774FA7623FF3F25982F803" xlink:to="loc_srt_MaximumMember_F27900E2262F251326BBF3F25982E4D4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/InvestmentSecuritiesNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/InvestmentSecuritiesTableDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_B8CACAEDEA01C569F45CC6F7E3E28113" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_D744FE041DE48F452C88C6F7E3E04A44" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_B8CACAEDEA01C569F45CC6F7E3E28113" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_D744FE041DE48F452C88C6F7E3E04A44" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_9306D68E06B2E72169FBC6F7E3E13124" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_D744FE041DE48F452C88C6F7E3E04A44" xlink:to="loc_us-gaap_InvestmentTypeAxis_9306D68E06B2E72169FBC6F7E3E13124" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_D9D588DEEC554B5CB944C6F7E3E1E376_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_9306D68E06B2E72169FBC6F7E3E13124" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_D9D588DEEC554B5CB944C6F7E3E1E376_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_D9D588DEEC554B5CB944C6F7E3E1E376" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_9306D68E06B2E72169FBC6F7E3E13124" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_D9D588DEEC554B5CB944C6F7E3E1E376" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_AvailableforsaleDebtSecurityCurrentMember" xlink:label="loc_icui_AvailableforsaleDebtSecurityCurrentMember_7926F054D6E392053FB8C6F7E3E14612" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_D9D588DEEC554B5CB944C6F7E3E1E376" xlink:to="loc_icui_AvailableforsaleDebtSecurityCurrentMember_7926F054D6E392053FB8C6F7E3E14612" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_708E0712E79F8746F288C6F7E3E28B4E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_B8CACAEDEA01C569F45CC6F7E3E28113" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtSecuritiesCurrent_708E0712E79F8746F288C6F7E3E28B4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss" xlink:label="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_29A912CF86755974C58EC6F7E3E3E3AB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_B8CACAEDEA01C569F45CC6F7E3E28113" xlink:to="loc_us-gaap_DebtSecuritiesAvailableForSaleContinuousUnrealizedLossPositionLessThan12MonthsAccumulatedLoss_29A912CF86755974C58EC6F7E3E3E3AB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_5EB5FDE60894A8AE7312C6F7E3E3E5AD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_B8CACAEDEA01C569F45CC6F7E3E28113" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesDebtMaturitiesWithinOneYearFairValue_5EB5FDE60894A8AE7312C6F7E3E3E5AD" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/InvestmentSecuritiesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesAssetsAndLiabilitiesLesseeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesCashFlowOperatingActivitiesLesseeDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesMaturityDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesMaturityTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesSupplementalBalanceSheetTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesSupplementalCashFlowTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LeasesTextDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionLineItems" xlink:label="loc_us-gaap_LesseeLeaseDescriptionLineItems_F944594CBF304CBE4C5E650873BECB18" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="loc_us-gaap_LesseeLeaseDescriptionTable_36AB8801D94299771BDA650873BC4094" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_F944594CBF304CBE4C5E650873BECB18" xlink:to="loc_us-gaap_LesseeLeaseDescriptionTable_36AB8801D94299771BDA650873BC4094" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_B3809D294F7EE8E98956650873BCBF90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LesseeLeaseDescriptionTable_36AB8801D94299771BDA650873BC4094" xlink:to="loc_srt_RangeAxis_B3809D294F7EE8E98956650873BCBF90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_B3809D294F7EE8E98956650873BCBF90" xlink:to="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_B3809D294F7EE8E98956650873BCBF90" xlink:to="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_88E73BA8A35BEEA90ED5650873BD679C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55" xlink:to="loc_srt_MinimumMember_88E73BA8A35BEEA90ED5650873BD679C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_A048D3F1690890F43800650873BE0AE3" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_8D9019B420512B0B9262650873BDFA55" xlink:to="loc_srt_MaximumMember_A048D3F1690890F43800650873BE0AE3" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_Optiontoextendinyears" xlink:label="loc_icui_Optiontoextendinyears_C2BF01F6EAF0F5FD8BEC650873BEB9F9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_F944594CBF304CBE4C5E650873BECB18" xlink:to="loc_icui_Optiontoextendinyears_C2BF01F6EAF0F5FD8BEC650873BEB9F9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LesseeOperatingLeaseTermOfContract" xlink:label="loc_us-gaap_LesseeOperatingLeaseTermOfContract_2CA60C673F4E2F88AF9D650873BFBB1F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LesseeLeaseDescriptionLineItems_F944594CBF304CBE4C5E650873BECB18" xlink:to="loc_us-gaap_LesseeOperatingLeaseTermOfContract_2CA60C673F4E2F88AF9D650873BFBB1F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/LongTermObligationsTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_324F23AB728532274D63F3F259448562" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_324F23AB728532274D63F3F259448562" xlink:to="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_BB602380189044584311F3F25944080C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_BB602380189044584311F3F25944080C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6C47EF6DBBE65B9797D1F3F2594477DE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_BB602380189044584311F3F25944080C" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6C47EF6DBBE65B9797D1F3F2594477DE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6C47EF6DBBE65B9797D1F3F2594477DE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_BB602380189044584311F3F25944080C" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6C47EF6DBBE65B9797D1F3F2594477DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_EDDD4C11FD7A6CEE6D53F3F25944DB94" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:to="loc_us-gaap_DebtInstrumentAxis_EDDD4C11FD7A6CEE6D53F3F25944DB94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0BDE1E1EBA318D3A190FF3F259447A52_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_EDDD4C11FD7A6CEE6D53F3F25944DB94" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0BDE1E1EBA318D3A190FF3F259447A52_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_0BDE1E1EBA318D3A190FF3F259447A52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_EDDD4C11FD7A6CEE6D53F3F25944DB94" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_0BDE1E1EBA318D3A190FF3F259447A52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateAxis" xlink:label="loc_us-gaap_VariableRateAxis_AFA7E7058A5A965364CFF3F25944B312" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:to="loc_us-gaap_VariableRateAxis_AFA7E7058A5A965364CFF3F25944B312" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_43198434FB8030238D80F3F25944C4F8_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_VariableRateAxis_AFA7E7058A5A965364CFF3F25944B312" xlink:to="loc_us-gaap_VariableRateDomain_43198434FB8030238D80F3F25944C4F8_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_VariableRateDomain" xlink:label="loc_us-gaap_VariableRateDomain_43198434FB8030238D80F3F25944C4F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_VariableRateAxis_AFA7E7058A5A965364CFF3F25944B312" xlink:to="loc_us-gaap_VariableRateDomain_43198434FB8030238D80F3F25944C4F8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodAxis" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_316567C2C6BFE9D1F768F3F25944B08D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_316567C2C6BFE9D1F768F3F25944B08D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87CCCD61F74E2FC6417BF3F25944A978_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_316567C2C6BFE9D1F768F3F25944B08D" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87CCCD61F74E2FC6417BF3F25944A978_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentRedemptionPeriodDomain" xlink:label="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87CCCD61F74E2FC6417BF3F25944A978" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentRedemptionPeriodAxis_316567C2C6BFE9D1F768F3F25944B08D" xlink:to="loc_us-gaap_DebtInstrumentRedemptionPeriodDomain_87CCCD61F74E2FC6417BF3F25944A978" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_50B49962409903D11641F3F25944889F" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_85452EEC8B0F2AA6CC23F3F2594432AE" xlink:to="loc_srt_RangeAxis_50B49962409903D11641F3F25944889F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_2A4D50F3EFA9C2F99C94F3F2594425D4_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_50B49962409903D11641F3F25944889F" xlink:to="loc_srt_RangeMember_2A4D50F3EFA9C2F99C94F3F2594425D4_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_2A4D50F3EFA9C2F99C94F3F2594425D4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_50B49962409903D11641F3F25944889F" xlink:to="loc_srt_RangeMember_2A4D50F3EFA9C2F99C94F3F2594425D4" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/NetIncomePerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/NetIncomePerShareDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable" xlink:label="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BF8A232BE18F1EB44E35F3F259A263E0" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BF8A232BE18F1EB44E35F3F259A263E0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0AB105A0F8DF5D51CAD2F3F259A2BBA5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareTable_BF8A232BE18F1EB44E35F3F259A263E0" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0AB105A0F8DF5D51CAD2F3F259A2BBA5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_442BE2AC4C6F6DBEF728F3F259A279A2_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0AB105A0F8DF5D51CAD2F3F259A2BBA5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_442BE2AC4C6F6DBEF728F3F259A279A2_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesNameDomain" xlink:label="loc_us-gaap_AntidilutiveSecuritiesNameDomain_442BE2AC4C6F6DBEF728F3F259A279A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareByAntidilutiveSecuritiesAxis_0AB105A0F8DF5D51CAD2F3F259A2BBA5" xlink:to="loc_us-gaap_AntidilutiveSecuritiesNameDomain_442BE2AC4C6F6DBEF728F3F259A279A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_BBA580D5E6D18B889B84F3F259A24885" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_BBA580D5E6D18B889B84F3F259A24885" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_3E1A063B076696C47E1DF3F259A2D18E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_ProfitLoss_3E1A063B076696C47E1DF3F259A2D18E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_6DF1AC178102321AD877F3F259A2BAB5" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_6DF1AC178102321AD877F3F259A2BAB5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements" xlink:label="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_D011719C1AE8361B51E6F3F259A20451" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_IncrementalCommonSharesAttributableToShareBasedPaymentArrangements_D011719C1AE8361B51E6F3F259A20451" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_F233105FF03531A4B513F3F259A2D8B7" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_F233105FF03531A4B513F3F259A2D8B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareBasic" xlink:label="loc_us-gaap_EarningsPerShareBasic_5C4A1DA43F5EC5B08FA2F3F259A21A7F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_EarningsPerShareBasic_5C4A1DA43F5EC5B08FA2F3F259A21A7F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="loc_us-gaap_EarningsPerShareDiluted_E78CBF60DCFC1CA034F6F3F259A2EAF6" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareLineItems_327A4859B46F0E2E9A87F3F259A27CDD" xlink:to="loc_us-gaap_EarningsPerShareDiluted_E78CBF60DCFC1CA034F6F3F259A2EAF6" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/NetIncomePerShareDetails1" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/NetIncomePerShareTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/NewAccountingPronouncements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/NewAccountingPronouncementsNewAccountingPronouncementsAdoptedPolicies" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsPrepaidsAndOtherAssetsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsRelatedPartyReceivableDetailsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_164E36484B5DAB100FD3F3F259820361" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5284C9AED0CB84F387AF3F259828B94" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_164E36484B5DAB100FD3F3F259820361" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5284C9AED0CB84F387AF3F259828B94" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByAssetClassAxis" xlink:label="loc_us-gaap_FairValueByAssetClassAxis_0DA5382BBCE5A7F36D37F3F25982A52B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5284C9AED0CB84F387AF3F259828B94" xlink:to="loc_us-gaap_FairValueByAssetClassAxis_0DA5382BBCE5A7F36D37F3F25982A52B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_99CC3606FC15CCC191EBF3F25982BB50_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_0DA5382BBCE5A7F36D37F3F25982A52B" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_99CC3606FC15CCC191EBF3F25982BB50_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain" xlink:label="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_99CC3606FC15CCC191EBF3F25982BB50" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByAssetClassAxis_0DA5382BBCE5A7F36D37F3F25982A52B" xlink:to="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_99CC3606FC15CCC191EBF3F25982BB50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_39E504B625B75E73E9D9F3F25982FE95" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsMeasuredOnRecurringBasisUnobservableInputReconciliationByAssetClassDomain_99CC3606FC15CCC191EBF3F25982BB50" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_39E504B625B75E73E9D9F3F25982FE95" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsRelatedPartyTextDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_6002DF16D4C5066E2E87F3F2574EF0EF" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3D1CEA95199A96826E14F3F2574DC5AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_6002DF16D4C5066E2E87F3F2574EF0EF" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3D1CEA95199A96826E14F3F2574DC5AA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionAxis_D4C68F9FB9785B373096F3F2574EDB16" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_3D1CEA95199A96826E14F3F2574DC5AA" xlink:to="loc_us-gaap_RelatedPartyTransactionAxis_D4C68F9FB9785B373096F3F2574EDB16" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_B48CAC829B69ACF0774FF3F2574EB2FE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_D4C68F9FB9785B373096F3F2574EDB16" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_B48CAC829B69ACF0774FF3F2574EB2FE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RelatedPartyTransactionDomain" xlink:label="loc_us-gaap_RelatedPartyTransactionDomain_B48CAC829B69ACF0774FF3F2574EB2FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionAxis_D4C68F9FB9785B373096F3F2574EDB16" xlink:to="loc_us-gaap_RelatedPartyTransactionDomain_B48CAC829B69ACF0774FF3F2574EB2FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember" xlink:label="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_77F1EB0E4FA61B3B822BF3F2574E3443" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionDomain_B48CAC829B69ACF0774FF3F2574EB2FE" xlink:to="loc_us-gaap_PrepaidExpensesAndOtherCurrentAssetsMember_77F1EB0E4FA61B3B822BF3F2574E3443" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PrepaidsAndOtherCurrentAssetsTextDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableLineItems_11F7A7C93981D9402428F3F2588787F0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionEquityInterestIssuedOrIssuableTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionEquityInterestIssuedOrIssuableTable_3F1B83B9E3265BF52891F3F25886D450" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionEquityInterestsIssuedOrIssuableLineItems_11F7A7C93981D9402428F3F2588787F0" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionEquityInterestIssuedOrIssuableTable_3F1B83B9E3265BF52891F3F25886D450" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_095904B57540251EFFFCF3F2588655EC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionEquityInterestIssuedOrIssuableTable_3F1B83B9E3265BF52891F3F25886D450" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_095904B57540251EFFFCF3F2588655EC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D22DB5361C9E245AAA96F3F258878A4F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_095904B57540251EFFFCF3F2588655EC" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D22DB5361C9E245AAA96F3F258878A4F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D22DB5361C9E245AAA96F3F258878A4F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_095904B57540251EFFFCF3F2588655EC" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_D22DB5361C9E245AAA96F3F258878A4F" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PropertyAndEquipment" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PropertyAndEquipmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1FFA42663B598C9DDAACF3F259B1766D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1FFA42663B598C9DDAACF3F259B1766D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_D2856F1EEF35FF9C7733F3F259B188B7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_1FFA42663B598C9DDAACF3F259B1766D" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_D2856F1EEF35FF9C7733F3F259B188B7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_D2856F1EEF35FF9C7733F3F259B188B7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_D2856F1EEF35FF9C7733F3F259B188B7" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LandBuildingsAndImprovementsMember" xlink:label="loc_us-gaap_LandBuildingsAndImprovementsMember_C15B516CC04D0F51C9E4F3F259B13139" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:to="loc_us-gaap_LandBuildingsAndImprovementsMember_C15B516CC04D0F51C9E4F3F259B13139" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_MoldsMember" xlink:label="loc_icui_MoldsMember_603714F48A9BA8DE8B67F3F259B1E55C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:to="loc_icui_MoldsMember_603714F48A9BA8DE8B67F3F259B1E55C" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_ComputerEquipmentAndSoftwareMember" xlink:label="loc_icui_ComputerEquipmentAndSoftwareMember_693C7249AAAA04B22EDCF3F259B1F15D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:to="loc_icui_ComputerEquipmentAndSoftwareMember_693C7249AAAA04B22EDCF3F259B1F15D" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_InstrumentsPlacedwithCustomersMember" xlink:label="loc_icui_InstrumentsPlacedwithCustomersMember_F4EE53DBED6C329FC29CF3F259B11AC1" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_B702DBEADCEF0B7B4B80F3F259B13185" xlink:to="loc_icui_InstrumentsPlacedwithCustomersMember_F4EE53DBED6C329FC29CF3F259B11AC1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_7BAB07AF2FCA403F7877F3F259B1F434" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_7BAB07AF2FCA403F7877F3F259B1F434" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_CA43D6712291AEA198A6F3F259B18A43" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_CA43D6712291AEA198A6F3F259B18A43" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_3968FC02C00C149B74DAF3F259B13AD4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_3968FC02C00C149B74DAF3F259B13AD4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MachineryAndEquipmentGross" xlink:label="loc_us-gaap_MachineryAndEquipmentGross_FD1BD383ABC489400C71F3F259B1EE63" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_MachineryAndEquipmentGross_FD1BD383ABC489400C71F3F259B1EE63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FurnitureAndFixturesGross" xlink:label="loc_us-gaap_FurnitureAndFixturesGross_F15CBEC85B9F53A88BC0F3F259B1E278" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_FurnitureAndFixturesGross_F15CBEC85B9F53A88BC0F3F259B1E278" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ConstructionInProgressGross" xlink:label="loc_us-gaap_ConstructionInProgressGross_7921FADE88DF720EFB74F3F259B129B7" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_955D4D4BDFFF68086FE1F3F259B1DDFC" xlink:to="loc_us-gaap_ConstructionInProgressGross_7921FADE88DF720EFB74F3F259B129B7" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/PropertyAndEquipmentTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/PropertyAndEquipmentTextDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_1D792B6B2CE74920846AE083B349A452" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_1D792B6B2CE74920846AE083B349A452" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_0CEBA13B6FB19A5F9982E083B3407960" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_srt_ConsolidationItemsAxis_0CEBA13B6FB19A5F9982E083B3407960" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_2CF8DD0085717249B3F9E083B3402339_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_0CEBA13B6FB19A5F9982E083B3407960" xlink:to="loc_srt_ConsolidationItemsDomain_2CF8DD0085717249B3F9E083B3402339_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_2CF8DD0085717249B3F9E083B3402339" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_0CEBA13B6FB19A5F9982E083B3407960" xlink:to="loc_srt_ConsolidationItemsDomain_2CF8DD0085717249B3F9E083B3402339" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_675ED0E0E5FB1BA86CB4E083B34005D9" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_675ED0E0E5FB1BA86CB4E083B34005D9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_EF61D5F4701DE8AA0611E083B34156EE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_675ED0E0E5FB1BA86CB4E083B34005D9" xlink:to="loc_us-gaap_SegmentDomain_EF61D5F4701DE8AA0611E083B34156EE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_EF61D5F4701DE8AA0611E083B34156EE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_675ED0E0E5FB1BA86CB4E083B34005D9" xlink:to="loc_us-gaap_SegmentDomain_EF61D5F4701DE8AA0611E083B34156EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_53490A811AF5638A2526E083B3410AF4" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_53490A811AF5638A2526E083B3410AF4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_426D9CCD1C969DAF287CE083B3410A91_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_53490A811AF5638A2526E083B3410AF4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_426D9CCD1C969DAF287CE083B3410A91_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_426D9CCD1C969DAF287CE083B3410A91" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_53490A811AF5638A2526E083B3410AF4" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_426D9CCD1C969DAF287CE083B3410A91" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_2A3E2A69C4B8EFA11505E083B3465302" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_2A3E2A69C4B8EFA11505E083B3465302" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_2A3E2A69C4B8EFA11505E083B3465302" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_2A3E2A69C4B8EFA11505E083B3465302" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EmployeeSeveranceMember" xlink:label="loc_us-gaap_EmployeeSeveranceMember_77BCBAD5F79460973A79E083B347674A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE" xlink:to="loc_us-gaap_EmployeeSeveranceMember_77BCBAD5F79460973A79E083B347674A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SpecialTerminationBenefitsMember" xlink:label="loc_us-gaap_SpecialTerminationBenefitsMember_B41EB22F85ACBF5BC6DFE083B3477C20" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE" xlink:to="loc_us-gaap_SpecialTerminationBenefitsMember_B41EB22F85ACBF5BC6DFE083B3477C20" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FacilityClosingMember" xlink:label="loc_us-gaap_FacilityClosingMember_0AB02D101F15FFB36739E083B3479AD0" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_9B628E97AA91C01B19EDE083B3476FEE" xlink:to="loc_us-gaap_FacilityClosingMember_0AB02D101F15FFB36739E083B3479AD0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanAxis" xlink:label="loc_us-gaap_RestructuringPlanAxis_FFCC76DA3F4FC660F711E083B3488438" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_RestructuringPlanAxis_FFCC76DA3F4FC660F711E083B3488438" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanDomain" xlink:label="loc_us-gaap_RestructuringPlanDomain_CADC0F6A13C5B1AB9592E083B348B644_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_FFCC76DA3F4FC660F711E083B3488438" xlink:to="loc_us-gaap_RestructuringPlanDomain_CADC0F6A13C5B1AB9592E083B348B644_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanDomain" xlink:label="loc_us-gaap_RestructuringPlanDomain_CADC0F6A13C5B1AB9592E083B348B644" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_FFCC76DA3F4FC660F711E083B3488438" xlink:to="loc_us-gaap_RestructuringPlanDomain_CADC0F6A13C5B1AB9592E083B348B644" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_80BE58F9F0596C95E716E083B348648E" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_80BE58F9F0596C95E716E083B348648E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_970F9517F1576DB4F9D4E083B348E64F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_80BE58F9F0596C95E716E083B348648E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_970F9517F1576DB4F9D4E083B348E64F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_970F9517F1576DB4F9D4E083B348E64F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_80BE58F9F0596C95E716E083B348648E" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_970F9517F1576DB4F9D4E083B348E64F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_2C513F7268AA0155FFBDE083B348113F" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_5FF8FC40BE4F190ED70FE083B33FBE2C" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_2C513F7268AA0155FFBDE083B348113F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_93866B114A3A9AE43F74E083B349F1DB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_2C513F7268AA0155FFBDE083B348113F" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_93866B114A3A9AE43F74E083B349F1DB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_93866B114A3A9AE43F74E083B349F1DB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_2C513F7268AA0155FFBDE083B348113F" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_93866B114A3A9AE43F74E083B349F1DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringReserve" xlink:label="loc_us-gaap_RestructuringReserve_2667A19DD803D0ED8AD4E083B349558F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_1D792B6B2CE74920846AE083B349A452" xlink:to="loc_us-gaap_RestructuringReserve_2667A19DD803D0ED8AD4E083B349558F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_A3F746E1C428E86954DFE083B34A79EE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_1D792B6B2CE74920846AE083B349A452" xlink:to="loc_us-gaap_RestructuringCharges_A3F746E1C428E86954DFE083B34A79EE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsForRestructuring" xlink:label="loc_us-gaap_PaymentsForRestructuring_95E6EFE752F4F29F2C6EE083B34A1DDE" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_1D792B6B2CE74920846AE083B349A452" xlink:to="loc_us-gaap_PaymentsForRestructuring_95E6EFE752F4F29F2C6EE083B34A1DDE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationNotes" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_E7C3EB9AEC2120663E6AF3F2568DA590" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_E7C3EB9AEC2120663E6AF3F2568DA590" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_869A24F5FD08982B5433F3F2568A5304" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_srt_ConsolidationItemsAxis_869A24F5FD08982B5433F3F2568A5304" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_F8615FC13834AB0419CAF3F2568AC0FA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_869A24F5FD08982B5433F3F2568A5304" xlink:to="loc_srt_ConsolidationItemsDomain_F8615FC13834AB0419CAF3F2568AC0FA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_F8615FC13834AB0419CAF3F2568AC0FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_869A24F5FD08982B5433F3F2568A5304" xlink:to="loc_srt_ConsolidationItemsDomain_F8615FC13834AB0419CAF3F2568AC0FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_E93D0C85D83FC6922849F3F2568BC0CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_E93D0C85D83FC6922849F3F2568BC0CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_48C6A1FFB1D4D6D1E3B9F3F2568B891B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E93D0C85D83FC6922849F3F2568BC0CE" xlink:to="loc_us-gaap_SegmentDomain_48C6A1FFB1D4D6D1E3B9F3F2568B891B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_48C6A1FFB1D4D6D1E3B9F3F2568B891B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_E93D0C85D83FC6922849F3F2568BC0CE" xlink:to="loc_us-gaap_SegmentDomain_48C6A1FFB1D4D6D1E3B9F3F2568B891B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_F32CC77354837E7EFA8DF3F2568BFD94" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_F32CC77354837E7EFA8DF3F2568BFD94" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_079606108F90F7F3D0D4F3F2568B18D3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_F32CC77354837E7EFA8DF3F2568BFD94" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_079606108F90F7F3D0D4F3F2568B18D3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_079606108F90F7F3D0D4F3F2568B18D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_F32CC77354837E7EFA8DF3F2568BFD94" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_079606108F90F7F3D0D4F3F2568B18D3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_573C101188AC0AC2F419F3F2568B9300" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_573C101188AC0AC2F419F3F2568B9300" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_273F186AF5D95BA32AE1F3F2568C6A30_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_573C101188AC0AC2F419F3F2568B9300" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_273F186AF5D95BA32AE1F3F2568C6A30_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_273F186AF5D95BA32AE1F3F2568C6A30" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_573C101188AC0AC2F419F3F2568B9300" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_273F186AF5D95BA32AE1F3F2568C6A30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanAxis" xlink:label="loc_us-gaap_RestructuringPlanAxis_9FDC3BB70F88EC6C6FFCF3F2568C1244" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_RestructuringPlanAxis_9FDC3BB70F88EC6C6FFCF3F2568C1244" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanDomain" xlink:label="loc_us-gaap_RestructuringPlanDomain_CECBCC48EBF54A5938DCF3F2568CD65A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringPlanAxis_9FDC3BB70F88EC6C6FFCF3F2568C1244" xlink:to="loc_us-gaap_RestructuringPlanDomain_CECBCC48EBF54A5938DCF3F2568CD65A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringPlanDomain" xlink:label="loc_us-gaap_RestructuringPlanDomain_CECBCC48EBF54A5938DCF3F2568CD65A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringPlanAxis_9FDC3BB70F88EC6C6FFCF3F2568C1244" xlink:to="loc_us-gaap_RestructuringPlanDomain_CECBCC48EBF54A5938DCF3F2568CD65A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="loc_us-gaap_IncomeStatementLocationAxis_3138EA68028442ACBCCEF3F2568DDEDE" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_IncomeStatementLocationAxis_3138EA68028442ACBCCEF3F2568DDEDE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_49188C7502F1244B32C3F3F2568D9207_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3138EA68028442ACBCCEF3F2568DDEDE" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_49188C7502F1244B32C3F3F2568D9207_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="loc_us-gaap_IncomeStatementLocationDomain_49188C7502F1244B32C3F3F2568D9207" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementLocationAxis_3138EA68028442ACBCCEF3F2568DDEDE" xlink:to="loc_us-gaap_IncomeStatementLocationDomain_49188C7502F1244B32C3F3F2568D9207" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationAxis" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_D9FF19D0882DCA4735C4F3F2568DC040" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_23B9BDBA978227D127CDF3F2568AA6AB" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_D9FF19D0882DCA4735C4F3F2568DC040" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_EA67192F75562D1B9580F3F2568DD9AC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_D9FF19D0882DCA4735C4F3F2568DC040" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_EA67192F75562D1B9580F3F2568DD9AC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLocationDomain" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_EA67192F75562D1B9580F3F2568DD9AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_OtherComprehensiveIncomeLocationAxis_D9FF19D0882DCA4735C4F3F2568DC040" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLocationDomain_EA67192F75562D1B9580F3F2568DD9AC" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationRestructuringStrategicTransactionAndIntegrationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationStrategicTransactionAndIntegrationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/RestructuringStrategicTransactionAndIntegrationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueContractLiabilitiesDetails" xlink:type="extended">
    <link:loc xlink:href="icui-20200331.xsd#icui_ContractassetandliabilitybalancesLineItems" xlink:label="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:type="locator" />
    <link:loc xlink:href="icui-20200331.xsd#icui_ContractassetandliabilitybalancesTable" xlink:label="loc_icui_ContractassetandliabilitybalancesTable_AEF8F5672AAA7BEE447CF3F259545114" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:to="loc_icui_ContractassetandliabilitybalancesTable_AEF8F5672AAA7BEE447CF3F259545114" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_6256842726A353453D11F3F259540781" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_icui_ContractassetandliabilitybalancesTable_AEF8F5672AAA7BEE447CF3F259545114" xlink:to="loc_srt_ProductOrServiceAxis_6256842726A353453D11F3F259540781" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_6256842726A353453D11F3F259540781" xlink:to="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_6256842726A353453D11F3F259540781" xlink:to="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_EquipmentrevenueMember" xlink:label="loc_icui_EquipmentrevenueMember_FFFCC818F1684A8127D8F3F25954240B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35" xlink:to="loc_icui_EquipmentrevenueMember_FFFCC818F1684A8127D8F3F25954240B" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_SoftwarerevenueMember" xlink:label="loc_icui_SoftwarerevenueMember_922A060E49A037E59975F3F25954CD56" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_77EAE5D3102F4A5B86CAF3F259547D35" xlink:to="loc_icui_SoftwarerevenueMember_922A060E49A037E59975F3F25954CD56" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MovementInDeferredRevenueRollForward" xlink:label="loc_us-gaap_MovementInDeferredRevenueRollForward_E3A5A361F8FE4C6C72F3F3F2595465E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:to="loc_us-gaap_MovementInDeferredRevenueRollForward_E3A5A361F8FE4C6C72F3F3F2595465E9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ContractWithCustomerLiability" xlink:label="loc_us-gaap_ContractWithCustomerLiability_1EA1F7764FCFC07DB444F3F25954B0DA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:to="loc_us-gaap_ContractWithCustomerLiability_1EA1F7764FCFC07DB444F3F25954B0DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DeferredRevenueAdditions" xlink:label="loc_us-gaap_DeferredRevenueAdditions_69122EBE40854F9D264DF3F25954FAF3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:to="loc_us-gaap_DeferredRevenueAdditions_69122EBE40854F9D264DF3F25954FAF3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInDeferredRevenue" xlink:label="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_0928F056272D93669800F3F25954CCEA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_icui_ContractassetandliabilitybalancesLineItems_D53BCD174F0EE729E250F3F25954A1DC" xlink:to="loc_us-gaap_IncreaseDecreaseInDeferredRevenue_0928F056272D93669800F3F25954CCEA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_D8A454EA6806B43113BBF3F256D93A49" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_C813BDF4908F6D6116D7F3F256D13359" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D8A454EA6806B43113BBF3F256D93A49" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_C813BDF4908F6D6116D7F3F256D13359" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_DC3AE1BECCC44D14A941F3F256D1F492" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_C813BDF4908F6D6116D7F3F256D13359" xlink:to="loc_srt_ProductOrServiceAxis_DC3AE1BECCC44D14A941F3F256D1F492" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_DC3AE1BECCC44D14A941F3F256D1F492" xlink:to="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_DC3AE1BECCC44D14A941F3F256D1F492" xlink:to="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_InfusionSystemsMember" xlink:label="loc_icui_InfusionSystemsMember_14B47F05D797A893E713F3F256D2AA87" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965" xlink:to="loc_icui_InfusionSystemsMember_14B47F05D797A893E713F3F256D2AA87" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_EquipmentrevenueMember" xlink:label="loc_icui_EquipmentrevenueMember_DDC8B1E9579A50CBB295F3F256D283FD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965" xlink:to="loc_icui_EquipmentrevenueMember_DDC8B1E9579A50CBB295F3F256D283FD" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_SoftwarerevenueMember" xlink:label="loc_icui_SoftwarerevenueMember_6B95F245BE2844A67A00F3F256D2C2DB" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_34182C906F5737B88BA8F3F256D2A965" xlink:to="loc_icui_SoftwarerevenueMember_6B95F245BE2844A67A00F3F256D2C2DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srt_StatementGeographicalAxis_1D1180A019409909CC65F3F256D3206D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_C813BDF4908F6D6116D7F3F256D13359" xlink:to="loc_srt_StatementGeographicalAxis_1D1180A019409909CC65F3F256D3206D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_538C0A6DB96F95002952F3F256D31B61_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_1D1180A019409909CC65F3F256D3206D" xlink:to="loc_srt_SegmentGeographicalDomain_538C0A6DB96F95002952F3F256D31B61_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_538C0A6DB96F95002952F3F256D31B61" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_1D1180A019409909CC65F3F256D3206D" xlink:to="loc_srt_SegmentGeographicalDomain_538C0A6DB96F95002952F3F256D31B61" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_BFE467C696C778DDC384F3F256D33033" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_C813BDF4908F6D6116D7F3F256D13359" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_BFE467C696C778DDC384F3F256D33033" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_843FB0C4E780FF4C68A4F3F256D8152D_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_BFE467C696C778DDC384F3F256D33033" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_843FB0C4E780FF4C68A4F3F256D8152D_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_843FB0C4E780FF4C68A4F3F256D8152D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_BFE467C696C778DDC384F3F256D33033" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_843FB0C4E780FF4C68A4F3F256D8152D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_50FA0834FFD119ADEB1BF3F256D93EE4" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D8A454EA6806B43113BBF3F256D93A49" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_50FA0834FFD119ADEB1BF3F256D93EE4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_B78BBB40CD7004251242F3F256D9EE1D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D8A454EA6806B43113BBF3F256D93A49" xlink:to="loc_us-gaap_Revenues_B78BBB40CD7004251242F3F256D9EE1D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenueByGeographyDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_E4DCB320CA35520F311CF3F25675B274" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_19C1B401AE76ED7CAF25F3F2567354BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_E4DCB320CA35520F311CF3F25675B274" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_19C1B401AE76ED7CAF25F3F2567354BF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srt_StatementGeographicalAxis_1E1819DD0549931C3E69F3F25673FFC2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_19C1B401AE76ED7CAF25F3F2567354BF" xlink:to="loc_srt_StatementGeographicalAxis_1E1819DD0549931C3E69F3F25673FFC2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_1E1819DD0549931C3E69F3F25673FFC2" xlink:to="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_1E1819DD0549931C3E69F3F25673FFC2" xlink:to="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EMEAMember" xlink:label="loc_us-gaap_EMEAMember_D74091FA8FD9210FCED6F3F25674D1E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:to="loc_us-gaap_EMEAMember_D74091FA8FD9210FCED6F3F25674D1E9" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_OtherforeigncountriesMember" xlink:label="loc_icui_OtherforeigncountriesMember_5100259FFEA648B69732F3F256741427" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:to="loc_icui_OtherforeigncountriesMember_5100259FFEA648B69732F3F256741427" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_ForeignMember" xlink:label="loc_icui_ForeignMember_2D34ECC7CBF8DC95D389F3F25674FCB9" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:to="loc_icui_ForeignMember_2D34ECC7CBF8DC95D389F3F25674FCB9" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="loc_country_US_424A6E5936A1EB97E033F3F25675F6B4" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_D3DD39DA3257BDF4961BF3F256745836" xlink:to="loc_country_US_424A6E5936A1EB97E033F3F25675F6B4" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_EF7A278339998F94E4EDF3F256753A54" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_E4DCB320CA35520F311CF3F25675B274" xlink:to="loc_us-gaap_Revenues_EF7A278339998F94E4EDF3F256753A54" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueDisaggregatedRevenueByProductLineDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_56CDED46F03507A65113F3F259441531" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_1D846593DC820AA25184F3F25944585C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_56CDED46F03507A65113F3F259441531" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_1D846593DC820AA25184F3F25944585C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="loc_srt_ProductOrServiceAxis_8143D4D6679E3CAF8EF7F3F259447E92" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_1D846593DC820AA25184F3F25944585C" xlink:to="loc_srt_ProductOrServiceAxis_8143D4D6679E3CAF8EF7F3F259447E92" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ProductOrServiceAxis_8143D4D6679E3CAF8EF7F3F259447E92" xlink:to="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ProductOrServiceAxis_8143D4D6679E3CAF8EF7F3F259447E92" xlink:to="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_InfusionConsumablesMember" xlink:label="loc_icui_InfusionConsumablesMember_786E4FA42A290980E891F3F259445E91" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:to="loc_icui_InfusionConsumablesMember_786E4FA42A290980E891F3F259445E91" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_IVSolutionsMember" xlink:label="loc_icui_IVSolutionsMember_58A91C0CBE6CA52E45DFF3F25944D83E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:to="loc_icui_IVSolutionsMember_58A91C0CBE6CA52E45DFF3F25944D83E" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_InfusionSystemsMember" xlink:label="loc_icui_InfusionSystemsMember_B51773AD10DD02698057F3F25944971F" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:to="loc_icui_InfusionSystemsMember_B51773AD10DD02698057F3F25944971F" xlink:type="arc" />
    <link:loc xlink:href="icui-20200331.xsd#icui_CriticalCareMember" xlink:label="loc_icui_CriticalCareMember_964E84AC965581CC7CE0F3F259440977" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ProductsAndServicesDomain_2FC7B335B32B92D4B863F3F2594481FA" xlink:to="loc_icui_CriticalCareMember_964E84AC965581CC7CE0F3F259440977" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_F7342F15F6F30B76CA14F3F25944F67B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_56CDED46F03507A65113F3F259441531" xlink:to="loc_us-gaap_Revenues_F7342F15F6F30B76CA14F3F25944F67B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/RevenueTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityAccumulatedOtherComprehensiveIncomeDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossTable" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_979B401CFD82AF002F4DF3F257AD00F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_979B401CFD82AF002F4DF3F257AD00F8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_3579D0AA9F7143ED5A53F3F257AD550E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossTable_979B401CFD82AF002F4DF3F257AD00F8" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_3579D0AA9F7143ED5A53F3F257AD550E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3579D0AA9F7143ED5A53F3F257AD550E" xlink:to="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_3579D0AA9F7143ED5A53F3F257AD550E" xlink:to="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedTranslationAdjustmentMember" xlink:label="loc_us-gaap_AccumulatedTranslationAdjustmentMember_B606896B5ECFEFA39A6FF3F257AE91A2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605" xlink:to="loc_us-gaap_AccumulatedTranslationAdjustmentMember_B606896B5ECFEFA39A6FF3F257AE91A2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember" xlink:label="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_14B4AB3271DF0AF7E5DEF3F257AEE4D1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605" xlink:to="loc_us-gaap_AccumulatedNetGainLossFromDesignatedOrQualifyingCashFlowHedgesMember_14B4AB3271DF0AF7E5DEF3F257AEE4D1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember" xlink:label="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_E7D0B66559230184CB8AF3F257AE5119" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_009D09BE6E981E94841FF3F257AE6605" xlink:to="loc_us-gaap_AccumulatedDefinedBenefitPlansAdjustmentMember_E7D0B66559230184CB8AF3F257AE5119" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_EC5C52501B61698B596CF3F257B450CF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_EC5C52501B61698B596CF3F257B450CF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_E4125DA9427564DF05C8F3F257B40D0E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossNetOfTax_E4125DA9427564DF05C8F3F257B40D0E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3F0BCD9C7F1870DC9D4EF3F257B579D8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax_3F0BCD9C7F1870DC9D4EF3F257B579D8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax_A8FFEDD4DF5B4D15536CF3F257B55F58" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeUnrealizedGainLossOnDerivativesArisingDuringPeriodNetOfTax_A8FFEDD4DF5B4D15536CF3F257B55F58" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax" xlink:label="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_129F717B28B4D0B4DA66F3F257B5D154" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax_129F717B28B4D0B4DA66F3F257B5D154" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax_5D2A9D269DC1048A758BF3F257B54136" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIOnDerivativesNetOfTax_5D2A9D269DC1048A758BF3F257B54136" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_6436F9E0D83FED7B82D6F3F257B514B3" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossReclassificationAdjustmentFromAOCIPensionAndOtherPostretirementBenefitPlansForNetGainLossNetOfTax_6436F9E0D83FED7B82D6F3F257B514B3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_6159A07ADA9FBECCDCABF3F257B5F3A3" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_6159A07ADA9FBECCDCABF3F257B5F3A3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent_BA07200C073EC2EBD709F3F257B579DA" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDerivativesQualifyingAsHedgesNetOfTaxPortionAttributableToParent_BA07200C073EC2EBD709F3F257B579DA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent" xlink:label="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_36896BFE3DE44CD3DDC7F3F257B65E27" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AccumulatedOtherComprehensiveIncomeLossLineItems_17D5D1A721FE459D5929F3F257B41FA4" xlink:to="loc_us-gaap_OtherComprehensiveIncomeDefinedBenefitPlansAdjustmentNetOfTaxPortionAttributableToParent_36896BFE3DE44CD3DDC7F3F257B65E27" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/StockholdersEquityTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsNotes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.icumed.com/role/SubsequentEventsTables" xlink:type="extended" />
</link:linkbase>
