lunatic

1 having or showing a very abnormal or sick state of mind he had a lunatic obsession with personal hygiene that was genuinely disturbing Synonyms balmy, barmy [chiefly British], bats, batty, bedlam, bonkers, brainsick, bughouse [slang], certifiable, crackbrained, cracked, crackers, crackpot, cranky [dialect], crazed, crazy, cuckoo, daffy, daft, demented, deranged, fruity [slang], gaga, haywire, kooky (also kookie), loco [slang], loony (also looney), loony tunes (or looney tunes), insane, mad, maniacal (also maniac), mental, meshuga (or meshugge also meshugah or meshuggah), moonstruck, non compos mentis, nuts, nutty, psycho, psychotic, scatty [chiefly British], screwy, unbalanced, unhinged, unsound, wacko (also whacko), wacky (also whacky), wud [chiefly Scottish]Related Words dotty, fey, loopy, off, potty [chiefly British], teched (or tetched), touched; aberrant, delirious, delusional, delusionary, disordered, disturbed, neurotic, obsessive-compulsive, paranoiac (also paranoic), paranoid (also paranoidal), schizoid, schizophrenic, sociopathic; eccentric, odd, oddball, pixilated (also pixillated), queer, strange; foolish, senseless, witless; irrational, unreasonable; amok (or amuck), ape, ballistic, bananas, berserk, nuclear; depressed; distracted, distraught, frantic, frenzied, haywire, hysterical (also hysteric), raving, wigged-out; fixated, monomaniac, monomaniacal, obsessedNear Antonyms clear, lucid, rational, reasonable; judicious, sensible, wise; healthy, normal, well-adjusted; unneuroticAntonyms balanced, compos mentis, sane, sound, uncrazy

2 showing or marked by a lack of good sense or judgment such lunatic clowning during church services is completely inappropriate Synonyms absurd, asinine, balmy, brainless, bubbleheaded, cockeyed, crackpot, crazy, cuckoo, daffy, daft, dippy, dotty, fatuous, featherheaded, fool, half-baked, harebrained, half-witted, inept, insane, jerky, kooky (also kookie), loony (also looney), foolish, lunkheaded, mad, nonsensical, nutty, preposterous, sappy, screwball, senseless, silly, simpleminded, stupid, tomfool, unwise, wacky (also whacky), weak-minded, witless, zanyRelated Words airheaded, birdbrained, boobish, brain-dead, chowderheaded, chuckleheaded, clueless, dense, dim, dim-witted, doltish, dopey (also dopy), dorky [slang], dull, dumb, dunderheaded, empty-headed, fatuous, feebleminded, gormless [chiefly British], idiotic (also idiotical), imbecile (or imbecilic), knuckleheaded, lamebrain (or lamebrained), mindless, moronic, oafish, obtuse, opaque, pinheaded, simple, slow, slow-witted, soft, softheaded, thoughtless, thick, thickheaded, unintelligent, vacuous, witless; fallacious, illogical, invalid, irrational, nonrational, surd, unreasonable, unreasoning, unsound, weak; farcical, laughable, ludicrous, ridiculous; notional; buffoonish, clownish; ill-advised, unconsidered, unreasonedNear Antonyms brainy, bright, clever, intelligent, smart; logical, rational, reasonable, valid; well-advisedAntonyms judicious, prudent, sagacious, sage, sane, sapient, sensible, sound, wise

1 a person judged to be legally or medically insane the lunatic was committed to an institution after running naked through the department store Synonyms bug, crackbrain, crazy, fool, fruitcake, head case, loon, loony, maniac, nut, nutcase, nutter [British slang], psycho, psychopath, sickie, sicko, wacko (also whacko) Related Words madman, madwoman; abnormal, deviant; manic-depressive, monomaniac, mythomaniac, neurotic, obsessive, obsessive-compulsive, paranoid, psychoneurotic, psychotic, schizo, schizoid, schizophrene, schizophrenic, sociopath; character, codger, crack, crackpot, crank, eccentric, fantastic (also fantastical), flake, kook, oddball, oddity, original, quiz, screwball, tyke (also tike) [chiefly British], weirdo, zany; case, patient

2 a person who lacks good sense or judgment we all knew she was a lunatic, but we never expected her to try to jump off of the roof of the school with a hang glider Synonyms berk [British], booby, charlie (also charley) [British], cuckoo, ding-a-ling, dingbat, ding-dong, dipstick, doofus [slang], featherhead, git [British], goose, half-wit, jackass, fool, mooncalf, nincompoop, ninny, ninnyhammer, nit [chiefly British], nitwit, nut, nutcase, simp, simpleton, turkey, yo-yoRelated Words daredevil; madman, madwoman; airhead, birdbrain, blockhead, cretin, dodo, dolt, donkey, dope, dork [slang], dumbbell, dummy, dunce, fathead, gander, goon, half-wit, idiot, ignoramus, imbecile, know-nothing, knucklehead, moron, numskull (or numbskull), pinhead, schlub (also shlub) [slang], schlump [slang], schnook [slang], stock; featherbrain, scatterbrain; butt, dupe, laughingstock, mockery, monkey; chump, loser, schlemiel (also shlemiel); character, codger, crackbrain, crackpot, crank, kook, oddball, screwball, weirdoNear Antonyms sage, thinker; brain, genius