insanity; mental disorder.

intermittent insanity, formerly believed to be related to phases of the moon.

extreme foolishness or an instance of it

Her decision to resign was sheer lunacy.

Law . unsoundness of mind sufficient to incapacitate one for civil transactions.

noun

saneness

noun

aberration , absurdity , alienation , asininity , dementia , derangement , distraction , fatuity , folly , foolhardiness , foolishness , idiocy , imbalance , imbecility , inanity , ineptitude , insanity , mania , psychopathy , psychosis , senselessness , silliness , stupidity , brainsickness , craziness , disturbance , insaneness , madness , mental illness , unbalance , foolery , nonsense , preposterousness , tomfoolery , zaniness