having a serious mental illness that makes a person lose touch with reality
Without his medication, the patient’s thoughts became wildly insane, and he could no longer tell what was real.
In the 19th century, many people who were considered insane were placed in large asylums outside the city.
✦ From Latin īnsānus, from in- “not” + sānus “healthy.”
extremely unreasonable, foolish, or dangerous
Driving through a blizzard with worn-out tires is insane.
It would be insane to invest all your savings in one risky stock.
extremely impressive, exciting, or great in amount
The crowd cheered after an insane dunk in the final seconds of the game.
Her guitar solo last night was insane—the notes flew by at lightning speed.
