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
Farlex Dictionary of Idioms.

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
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • (as) crazy as a bedbug
  • crazy as a bedbug
  • (as) crazy as a peach-orchard boar
  • crazy in the head
  • bedbug
  • peach
  • orchard
  • boar
  • loon
  • crazy as a betsy bug
References in classic literature
"Crazy as a loon," William sneered in open aside to the rest.
The Red One
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.
The Golden Road
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.
Review: Return of a gentle genius; JOHN PRINE Symphony Hall, Birmingham