Learner's definition of INSANE
1 [more insane; most insane] : not sane: such asa : having or showing severe mental illness
Usage The use of insane to describe a person with severe mental illness is now often considered offensive. The phrase mentally ill is preferred. Insane in this sense now occurs chiefly in such legal phrases as criminally insane and temporarily insane. b : unable to think in a clear or sensible way c — used in the phrase drive/make (someone) insane to describe annoying or bothering someone very much.
2 : wild and uncontrolled 3 [more insane; most insane] : very foolish or unreasonable 4 : used for people who have severe mental illnesses
: to become mentally ill: to go crazy— usually used in an exaggerated way
I must be going insane. I can't find my car keys anywhere.
If you don't stop making that noise, I'm going to go (completely) insane!
: insane people: people who have severe mental illness