insane

1 having or showing a very abnormal or sick state of mind only an insane person would intentionally jump off a skyscraper 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), lunatic, 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, obsessed Phrases around the bend, off one's gourd, off one's head, off one's rocker, out of one's head (or mind), out to lunch [slang] Near Antonyms clear, lucid, rational, reasonable; judicious, sensible, wise; healthy, normal, well-adjusted; unneurotic Antonyms balanced, compos mentis, sane, sound, uncrazy

2 conceived or made without regard for reason or reality a completely insane plan to build an opera house in the middle of nowhere Synonyms absurd, bizarre, crazy, fanciful, foolish, fantastic, nonsensical, preposterous, unreal, wildRelated Words implausible, inconceivable, incredible, unbelievable, unimaginable, unthinkable; extravagant, grotesque; bizarro, curious, eccentric, far-out, funny, kinky, kooky (also kookie), odd, outlandish, out-of-the-way, outré, peculiar, quaint, queer, queerish, quirky, screwy, strange, wacky (also whacky), way-out, weird; farcical, laughable, ludicrous, ridiculous; Alice-in-Wonderland, Kafkaesque, nightmarish; dreamlike, surrealAntonyms realistic, reasonable

3 showing or marked by a lack of good sense or judgment an insane plan to blow all of their savings on lottery tickets Synonyms absurd, asinine, balmy, brainless, bubbleheaded, cockeyed, crackpot, crazy, cuckoo, daffy, daft, dippy, dotty, fatuous, featherheaded, fool, half-baked, harebrained, half-witted, inept, foolish, jerky, kooky (also kookie), loony (also looney), lunatic, 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

4 going beyond a normal or acceptable limit in degree or amount wanted an insane amount of money to paint our house Synonyms baroque, devilish, exorbitant, extravagant, extreme, fancy, immoderate, inordinate, excessive, intolerable, lavish, overdue, overextravagant, overmuch, overweening, plethoric, steep, stiff, towering, unconscionable, undue, unmercifulRelated Words boundless, endless, immeasurable, infinite, limitless; unbearable, unjustifiable, unwarranted; improper, inappropriate, thick, unseemly; unrestrainedNear Antonyms deficient, inadequate, insufficient; minimal, minimumAntonyms middling, moderate, modest, reasonable, temperate