insane

/ɪnˈseɪn/

/ɪnˈseɪn/

Other forms: insanest; insaner

To be insane is to have a seriously disordered state of mind. This is also a slang word for acting wacky or wild.

This word has two closely related meanings. People who are insane are suffering from a seriously irrational or disordered state of mind. When someone commits a crime, it's important to know if they were sane or insane. If they're insane, the penalty is different. Many uses of the word are not so serious. A wild party is called insane, and car salesmen say their prices are insane. A teacher assigning six hours of homework might be told "That’s insane!"

Definitions of insane

1. adjective

   afflicted with or characteristic of mental derangement
   “was declared insane”

   “insane laughter”

   synonyms:

   irrational

   not consistent with or using reason

   unreasonable

   not reasonable; not showing good judgment

   amok, amuck, berserk, demoniac, demoniacal, possessed

   frenzied as if possessed by a demon

   around the bend, balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kookie, kooky, loco, loony, loopy, nuts, nutty, round the bend, wacky, whacky

   informal or slang terms for mentally irregular

   brainsick, crazy, demented, disturbed, mad, sick, unbalanced, unhinged

   affected with madness or insanity

   certifiable, certified

   fit to be certified as insane (and treated accordingly)

   crackbrained, idiotic

   insanely irresponsible

   crazed, deranged, half-crazed

   driven insane

   fey, touched

   slightly insane

   hebephrenic

   suffering from a form of schizophrenia characterized by foolish mannerisms and senseless laughter along with delusions and regressive behavior

   lunatic, moonstruck

   insane and believed to be affected by the phases of the moon

   maniac, maniacal

   wildly disordered

   manic-depressive

   suffering from a disorder characterized by alternating mania and depression

   maniclike

   resembling the mania of manic-depressive illness

   mentally ill, unsound, unstable

   suffering from severe mental illness

   non compos mentis, of unsound mind

   not of sound mind, memory, or understanding; in law, not competent to go to trial

   paranoid

   suffering from paranoia

   psychopathic, psychopathologic, psychopathological

   suffering from an undiagnosed mental disorder

   psychotic

   characteristic of or suffering from psychosis

   raving mad, wild

   talking or behaving irrationally

   schizophrenic

   suffering from some form of schizophrenia

   screw-loose, screwy

   not behaving normally

   antonyms:

   sane

   mentally healthy; free from mental disorder

   rational

   consistent with or based on or using reason

   compos mentis, of sound mind

   of sound mind, memory, and understanding; in law, competent to go to trial

   in her right mind, in his right mind, in their right minds

   behaving responsibly

   lucid

   having a clear mind
2. adjective

   very foolish
   “took insane risks behind the wheel”

   synonyms: harebrained, mad

   foolish

   devoid of good sense or judgment