fool, nincompoop, clown, simpleton

informal idiot, ninny, dope, dimwit, chump, goon, dumbo, dummy, halfwit, nitwit, dum-dum, loon, jackass, cretin, imbecile, jerk, nerd, fathead, blockhead, numbskull, dunderhead, dunce, dipstick, bonehead, chucklehead, clod, goop, knucklehead, lamebrain, pea-brain, pudding-head, thickhead, wooden-head, pinhead, airhead, birdbrain, dumb-bell, donkey, stupe, noodle

British informal nit, twit, numpty, clot, plonker, berk, prat, pillock, wally, git, wazzock, divvy, nerk, dork, twerp, charlie, mug, muppet

Scottish informal nyaff, balloon, sumph, gowk

Irish informal gobdaw

North American informal schmuck, bozo, boob, lamer, turkey, schlepper, chowderhead, dumbhead, goofball, goof, goofus, galoot, lummox, klutz, putz, schlemiel, sap, meatball, gink, cluck, clunk, ding-dong, dingbat, wiener, weeny, dip, simp, spud, coot, palooka, poop, squarehead, yo-yo, dingleberry

Australian/New Zealand informal drongo, dill, alec, galah, nong, bogan, poon, boofhead

South African informal mompara

British vulgar slang knobhead

North American vulgar slang asshat

dated tomfool, muttonhead, noddy

archaic clodpole, loggerhead, spoony, mooncalf