windfall . windfall {n.} An unexpected gift or gain of sizeable proportion. The unexpected retroactive pay raise was a most welcome windfall. Categories: add yours {n.} 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