Entry 1 sense Webster, 1913 Underwhelm /ŭnˌ-dẽrw-ĕlm'/ · Un·der·whelm · IPA /ˌʌndərwˈɛlm/ 01 v. t. To interest less than anticipated; to be dull to (a person). 1. To interest less than anticipated; to be dull to (a person).