moron

airhead, blockhead, chucklehead, dimwit, dodo, dolt, donkey, dope, dork [slang], dullard, dumbbell, dummy, dunce, fathead, goof, goon, half-wit, idiot, ignoramus, imbecile, know-nothing, knucklehead, lamebrain, loon, lunkhead, nincompoop, ninny, nitwit, noddy, noodle, numskull (or numbskull), oaf, pinhead, saphead, simpleton, stock, turkey, yahoo, yo-yo