Synonyms for Nitwit:

adj.

foolish (adjective)
dim-witted, blithering, ignorant, cretinous, lame-brained, moronic, asinine, dumb, bone-headed, half-witted, goofy, dopey, absurd, imbecilic, loony, foolish, doltish, inane, chuckle-headed, crackpot, knuckle-headed, blockheaded, meat-headed, dotty, crazy, brainless, nonsensical, idiotic.

n.

clown, maniac, dumb blond, numpty, joker. ding-dong, schmuck, goof, Mooncalf, tomfool, ninny, ability, nerd, turkey, jerk, gander, simple, schmo, goose, dip, softhead. fool (noun)
dolt, moron, dummy, half-wit, dimwit, nincompoop, bungler, imbecile, lame-brain, knuckle-head, fool, blockhead, chuckle-head, dumbbell, ignoramus, dunce, simpleton, loon, cretin, clod, bonehead, dullard, meathead.
idiot (noun)
dumbbell, fool, jerk, moron, ignoramus, dunce, bonehead, imbecile, dummy, ninny, blockhead, simpleton, dimwit, nincompoop, cretin.
ignoramus (noun)
buffoon, birdbrain, scatterbrain.
nitwit (noun)
doofus, dimwit, half-wit.
schmuck (noun)
schmuck.
stupid person (noun)
dolt, dunce.

Other synonyms:

ninny, schmuck, ding-dong, nerd, schmo, softhead, tomfool. Mooncalf, goof, goose, turkey. gander. simple. Other relevant words:
schmo, gander, doofus, jerk, goose, nerd, softhead, goof, tomfool, simple, turkey, schmuck, ninny, Mooncalf, clown, dip, ding-dong.