underinsured Syllabification: (un·der·in·sured)Pronunciation: /ˌəndərinˈSHo͝ord/Definition of underinsured adjective (of a person) having inadequate insurance coverage. Derivatives underinsurancePronunciation: /ˈəndərinˌSHo͝orəns/ noun underinsured in other Oxford dictionaries Definition of underinsured in the British & World English dictionary