insanity

1 a serious mental disorder that prevents one from living a safe and normal life his incurable insanity requires that he spend the rest of his life in a mental hospital Synonyms aberration, dementia, derangement, lunacy, madness, mania, rage [archaic] Related Words neurosis, psychosis; instability, irrationality, unreasonableness; delirium, frenzy, hysteria; hallucinosis, hypomania, paranoia, schizophrenia; senile dementia; delusion, hallucination; monomania, obsession, phobia; abnormality, dementedness, unsoundness Near Antonyms lucidity, rationality, rationalness, reasonability, reasonableness; normality, soundness Antonyms mind, saneness, sanity

2 a foolish act or idea everyone laughed at the latest insanity from the town eccentric Synonyms absurdity, asininity, bêtise, fatuity, foolery, foppery, idiocy, imbecility, inanity, folly, lunacy, stupidityRelated Words absurdness, craziness, foolishness, inaneness, madness, senselessness, witlessness; buffoonery, monkeyshine(s), shenanigan(s), tomfoolery; drivel, humbug, nonsense, twaddle; blunder, bungle, flub, goof, howlerNear Antonyms discretion, forethought, prudence, sagacity, wisdom; brainstorm, inspiration

3 lack of good sense or judgment had the insanity to think that taking over a government building in protest of our foreign policy was a good idea Synonyms absurdity, asininity, balminess, brainlessness, craziness, daftness, dippiness, dottiness, fatuity, fatuousness, folly, imbecility, inanity, foolishness, lunacy, madness, nonsensicalness, nuttiness, preposterousness, senselessness, silliness, simplicity, unwisdom, wackiness, witlessness, zaninessRelated Words denseness, dim-wittedness, doltishness, dopiness, dullness (also dulness), dumbness, feeblemindedness, gormlessness [chiefly British], idiocy, mindlessness, oafishness, obtuseness, simplemindedness, simpleness, slowness, stupidity, stupidness, vacuity; fallacy, irrationality, unreasonableness; kookiness, weirdness; laughableness, ludicrousness, ridiculousnessNear Antonyms logicality, logicalness, rationality, rationalness, reasonability, reasonableness, validity; discernment, insight, perception, percipienceAntonyms prudence, sagaciousness, sagacity, sageness, sanity, sapience, sensibleness, soundness, wisdom