grand slam . grand slam {n.} A home run hit when there are three men on the bases. Tony's grand slam won the game for the Yankees, 4—0. Categories: add yours {n.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: G Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Add my comment