Entry 1 sense Webster, 1913 nincompoop /nĭng'-kəm-po͞opˌ/ · nin·com·poop · IPA /ˈnɪŋkəmˌpup/ 01 n. A fool; a silly or stupid person. 1. A fool; a silly or stupid person.[Law] “An old ninnyhammer, a dotard, a nincompoop, is the best language she can afford me.” — Addison.