off one's head . off one's head {adj. phr.} Crazy; mad. We had no doubt that the old man was off his head when we saw him jumping into the lake with his winter coat on. Categories: add yours crazy doubt {adj. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: O Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Comment on this entry