Nincompoop
a person of subnormal intelligence
Synonyms
arse, blockhead, bonehead, changeling, chump, clot, dimwit, dolt, donkey, dope, dumbo, dummy, dunce, fathead, fat-head, Fool, goon, half-wit, Idiot, imbecile, lout, ninny, nitwit, numskull, nut, oaf, poop, retard, simpleton, wanker, berk, booby, bugger, burk, cretin, damn fool, dumbbell, ham