preposterous

1 conceived or made without regard for reason or reality the idea that extraterrestrials built the pyramids is preposterous Synonyms absurd, bizarre, crazy, fanciful, foolish, insane, nonsensical, fantastic, 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

2 showing or marked by a lack of good sense or judgment a preposterous suggestion to go swimming in this freezing weather 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), lunatic, lunkheaded, mad, nonsensical, nutty, foolish, 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

3 so foolish or pointless as to be worthy of scornful laughter the movie thriller had such a preposterous plot that we were on the edge of our seats snickering Synonyms absurd, cockamamy (or cockamamie), comical, derisive, derisory, farcical, laughable, ludicrous, pathetic, ridiculous, risible, sillyRelated Words asinine, brainless, dumb, fatuous, foolish, half-baked, half-witted, harebrained, idiotic (also idiotical), imbecile (or imbecilic), inane, jerky, moronic, nonsensical, simpleminded, stupid, unwise, weak-minded, witless; balmy, cockeyed, crazy, cuckoo, daffy, daft, dotty, insane, kooky (also kookie), loony (also looney), lunatic, mad, nutty, screwball, senseless, wacky (also whacky); fantastic (also fantastical), far-fetched, inconceivable, incredible, unbelievable, unreal, unrealistic, unreasonable; illogical, irrationalNear Antonyms earnest, serious, solemn; believable, conceivable, credible, logical, rational, realistic, reasonable, sensible