n. pl. in·san·i·ties 1. Severe mental illness or derangement. Not used in psychiatric diagnosis. 2. Law a. Unsoundness of mind sufficient to render a person unfit to maintain a contractual or other legal relationship or sufficient to warrant commitment to a mental health facility. b. Incapacity to form the criminal intent necessary for legal responsibility, as when a mental disorder prevents a person from knowing the difference between right and wrong. c. Incapacity because of a mental disorder to participate adequately as a defendant in criminal proceedings or to understand the imposition of a criminal punishment, particularly the death penalty. 3. a. Extreme foolishness or irrationality: "The insanity of sending troops into Russia when European peace looked imminent horrified him" (Mary V. Dearborn). b. Something that is extremely foolish, distinctly irrational, or wildly excited: "twisted forms of musical insanity" (Christopher J. Kelter). |
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