letdown letdown {n.} A disappointment; a heartbreak. It was a major letdown for John when Mary refused to marry him. Categories: add yours add yours disappointment {n.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 » In RussianTo section: L Subscribe to: American Idioms► Also consider the parent subscriptions (3)Idioms feedEnglish languageHome page and general feed Discuss Discuss