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1. Relatively permanent disorder of the mind
   - madness, craziness [informal]
    
2. The quality of being rash and foolish
   "he lived on a knife-edge between genius and insanity";
   - folly, foolishness, craziness, madness, nuttiness [informal]

Derived forms: insanities

Type of: daftness [informal], mental disease, mental illness, psychopathy, stupidity

Antonym: sanity

Encyclopedia: Insanity