insane

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?

And you told me not to drive But I made it home alive So you said that only proves that I'm insane

Used by or relating to insane people.

an insane hospital

an insane asylum

Causing insanity or madness.

Were such things here, as we doe speake about? / Or haue we eaten on the insane Root, / That takes the Reason Prisoner?

Characterized by excess or the utmost folly; ridiculous; impractical.

an insane plan

an insane amount of money

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."