Source : Webster's Revised Unabridged Dictionary (1913)

Half-wit \Half"-wit`\, n.
   A foolish; a dolt; a blockhead; a dunce. --Dryden.

Source : WordNet®

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