when hell freezes over when hell freezes over {adv. phr.}, {slang} Never. I'll believe you when hell freezes over. Contrast: UNTIL HELL FREEZES OVER. Categories: add yours {adv. phr.} {slang} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: W Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Comment on this entry