turn tail . turn tail {v. phr.}, {informal} To run away from trouble or danger. When the bully saw my big brother, he turned tail and ran. Categories: add yours {informal} {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: T Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Leave my opinion