definition insane
Definition of insane. 1  1a (1) : exhibiting a severely disordered state of mind : affected with mental illness (2) law : affected with insanity (see insanity 2) criminally insaneb : unable to think in a clear or sensible way : crazy insane with jealousy ânot used technically. 2 : used by, typical of, or intended for mentally ill people an insane asylum.