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