Definition of: insane

(in·sān′) adjective
1. Not sane; mentally deranged or unsound; crazy; irrational.
2. Set apart for or used by the insane.
3. Characteristic of those who are mentally deranged; insensate.
4. Foolish, extravagant, or impractical: insane hopes. [<L insanus <in- not + sanus whole]
—in·sane′ly adverb
—in·sane′ness noun Synonyms: absurd, cracked, crazed, crazy, delirious, demented, deranged, distracted, frantic, frenzied, irrational, lunatic, mad, maniac, maniacal, monomaniac, wandering, wild. Antonyms: clear, collected, level–headed, sage, sane, sensible, sober, sound, wise.