half-wit

from WordNet (r) 3.0 (2006)

half-wit
    n 1: a person of subnormal intelligence [syn: {idiot},
         {imbecile}, {cretin}, {moron}, {changeling}, {half-wit},
         {retard}]
    2: a stupid incompetent person [syn: {dimwit}, {nitwit}, {half-
       wit}, {doofus}]

from The Collaborative International Dictionary of English v.0.48

Half-wit \Half"-wit`\ (-w[i^]t`), n.
   A foolish person; a dolt; a blockhead; a dunce. --Dryden.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

18 Moby Thesaurus words for "halfwit":
      ass, birdbrain, dolt, dullard, dunce, dunderhead, dunderpate, fool,
      idiot, imbecile, moron, nincompoop, ninny, nit, nitwit, numskull,
      simpleton, twit

[email protected]