crazy as a loon

crazy as a loon

Insane. Often used jocularly. Don't leave me alone with Uncle Stu, he's crazy as a loon!
See also: crazy, loon

crazy as a loon

AMERICAN, INFORMAL
If you describe someone as crazy as a loon, you mean that their behaviour is very strange or silly. She was obviously crazy as a loon.
See also: crazy, loon
References in classic literature ?
He took the measles when he was forty-five and was crazy as a loon with them, and the doctor ordered them to give him a dose of brandy.
Standouts from the album were Glory Of True Love, Crazy As A Loon and Long Monday, with superb harmonies from his guest, the marvellous Mindy Smith.