Simple Simon, block, blockhead, booby, brute, clod, cockamamie, cretin, cuckoo, dimwit, dolt, donkey, dope, driveler, dullard, dullhead, dumb cluck, dumbbell, dumbhead, dummkopf, dummy, dunce, featherbrain, fool, gaga, goose, gowk, half-wit, idiot, ignoramus, illiterate, imbecile, jay, jerk, jobbernowl, klutz, know-nothing, lackwit, lamebrain, looby, loon, lowbrow, lubber, mooncalf, moron, nincompoop, ninny, ninnyhammer, nitwit, noodle, nope, oaf, pinhead, put, rattlebrain, rattlehead, rattlepate, saphead, scatterbrain, silly billy, simpleton, witling

Boeotian, absent-minded, absurd, addlebrained, addled, addleheaded, addlepated, aimless, anserine, apish, asinine, asslike, backward, balmy, banal, barmy, batty, beef-brained, beef-witted, beetleheaded, befooled, beguiled, bemused, benumbed, besotted, bird-brained, bland, blank, blear-eyed, blear-witted, blockheaded, blockish, blunt, boneheaded, boorish, bootless, boring, bovine, brain-dead, brainless, brutish, buffoonish, bullheaded, bullish, careless, childish, chuckleheaded, chumpish, cloddish, cockeyed, comatose, commonplace, confused, cowish, crackbrained, cracked, crass, crazy, credulous, cretinous, cuckoo, daffy, daft, damfool, dazed, dazzled, deficient, dense, derisible, dill, dim-witted, dim, dimwitted, dizzy, doiled, doltish, dopey, doting, dozy, driftless, drugged, dull-witted, dull, dullard, dumb, duncical, duncish, dunderheaded, empty-headed, empty, excessive, extravagant, faineant, fat-witted, fat, fatheaded, fatuitous, fatuous, featherbrained, featherheaded, feeble-minded, flaky, fond, foolhardy, foolheaded, foolish, frivolous, frothy, fruitless, fuddled, futile, gaumless, giddy, glaikit, goofy, goosey, green, groggy, gross, groundless, gulled, gullible, half-assed, half-baked, half-witted, halfwitted, haphazard, harebrained, harum-scarum, heedless, ho-hum, humdrum, idiotic, idiotical, ignorant, ill-advised, ill-considered, ill-suited, illogical, imbecile, imbecilic, immature, impassive, improper, imprudent, in a daze, inane, inanimate, inappropriate, incogitant, incongruous, inconsequential, inconsistent, indiscreet, ineducable, inept, inert, infatuated, injudicious, insane, insensate, insensible, insipid, insulse, into a daze, into a stupor, into oblivion, intractable, irrational, irrelevant, irresponsible, jerky, klutzy, knocked silly, know-nothing, kooky, lackadaisical, lackwit, lame-brained, lamebrained, laughable, lazy, lethargic, lifeless, light-headed, light-minded, lightweight, loony, loopy, loutish, ludicrous, lumbering, lumpish, lunatic, mad, maudlin, meaningless, mercurial, mindless, monotonous, moronic, muddled, muddleheaded, mulish, muttonheaded, naive, nearsighted, noddy, nonsensical, noodle-headed, numb, numskulled, nutty, oafish, obdurate, obstinate, obtuse, opaque, ordinary, oxlike, pea-brained, pinhead, pointless, preposterous, profitless, prosaic, puerile, punchy, purposeless, rash, rattlebrained, rattleheaded, reckless, retarded, ridiculous, risible, sappy, scatterbrained, screwy, semiconscious, senseless, sentimental, shortsighted, silly, simple-minded, simple, simpleminded, slow-witted, slow, sluggish, slumberous, soft in the head, somnolent, soporific, sottish, spiritless, stolid, stubborn, stunned, stupefied, subnormal, superficial, tactless, tame, tedious, thick-witted, thick, thickheaded, thickskulled, thoughtless, tiresome, tiring, torpid, unbending, unconnected, unconscious, undiscriminating, unheeding, unimaginative, uninspired, unintelligent, uninteresting, unoccupied, unrealistic, unreasonable, unreasoning, unsophisticated, unteachable, unthinking, unwary, unwise, unwitty, unyielding, vacuous, vapid, void, wacky, weak-headed, weak-minded, wearing, wearish, wet, witless, wooden-headed, wrongheaded