'nincompoop' definitions:

Definition of 'nincompoop'

From: WordNet
noun
A stupid foolish person [syn: nincompoop, poop, ninny]

Definition of 'nincompoop'

From: GCIDE
  • nincompoop \nin"com*poop\, n. [A corruption of non compos.] A fool; a silly or stupid person. [Law] [1913 Webster]
  • An old ninnyhammer, a dotard, a nincompoop, is the best language she can afford me. --Addison. [1913 Webster]