lunacy

1 a foolish act or idea <you want to sneak into the building after the alarm is set—what lunacy!> Synonyms absurdity, asininity, bêtise, fatuity, foolery, foppery, idiocy, imbecility, inanity, insanity, folly, 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

2 a serious mental disorder that prevents one from living a safe and normal life <the judge ruled that the certified lunacy of the accused made him incompetent to stand trial> Synonyms aberration, dementia, derangement, insanity, 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, unsoundnessNear Antonyms lucidity, rationality, rationalness, reasonability, reasonableness; normality, soundnessAntonyms mind, saneness, sanity

3 lack of good sense or judgment <our friend's good-natured lunacy makes him of no use in an emergency but very entertaining companion nevertheless> Synonyms absurdity, asininity, balminess, brainlessness, craziness, daftness, dippiness, dottiness, fatuity, fatuousness, folly, imbecility, inanity, insanity, foolishness, 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