calm down . calm down {v. phr.} To become quiet; relax. "Calm down, Mr. Smith," the doctor said with a reassuring smile. "You are going to live a long time." Categories: add yours time {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: C Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Leave my opinion