insane

Etymology

From Latin īnsānus (“unsound in mind; mad, insane”), from in- + sānus (“sound, sane”).

adj

1. Exhibiting unsoundness or disorder of mind; not sane; utterly mad.
   What is the cause of insanity? Nobody can answer such a sweeping question as that, but we know that certain diseases, such as syphilis, break down and destroy the brain cells and result in insanity. In fact, about one-half of all mental diseases can be attributed to such physical causes as brain lesions, alcohol, toxins, and injuries. But the other half—and this is the appalling part of the story—the other half of the people who go insane apparently have nothing organically wrong with their brain cells. In post-mortem examinations, when their brain tissues are studied under the highest-powered microscopes, they are found to be apparently just as healthy as yours and mine. Why do these people go insane? 1936, Dale Carnegie, “Part 1, Chapter 2. THE BIG SECRET OF DEALING WITH PEOPLE”, in How to Win Friends and Influence People, page 41
2. Used by or relating to insane people.
   an insane hospital
   an insane asylum
3. Causing insanity or madness.
4. (informal) Characterized by insanity or the utmost folly; ridiculous; impractical.
   an insane plan
   an insane amount of money
5. (slang) Extremely good; incredibly amazing.
   That guy is insane at FPS games.
   Cederstrand was all over the ice, whipping his sled around and firing pucks into the net. It's what Straschnitzki is aiming for. "He's insane. The turns, the shots. It's something I want to do some day." 2018-08-08, Bill Graveland, “'I'll get better': Paralyzed Humboldt Broncos player working to improve at sledge hockey”, in CBC
   And fans echoed their responses. "You nailed it, girl! This movie is so special. Your work is insane! 💗," one person wrote. "Is there ANYTHING you can't do?! I'm impressed," said another. 2020-08-24, Nicol Natale, “Watch Reese Witherspoon Nail a Seriously Impressive Backflip in This Throwback Video”, in Prevention
   On getting two quick eliminations, SypherPK cries out ecstatically: This gun is insane, it's the best gun ever! Woohoo! 2020-09-19, Saahil Agnelo Periwal, “Fortnite Chapter 2 Season 4: SypherPK claims a Victory Royale by using the 'rarest' item in the game- The Galactus Gun”, in Sportskeeda