third base . third base {n.} The base to be touched third in baseball. He reached third base standing up on a long triple. Categories: add yours add yours {n.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: T Subscribe to: American Idioms► Also consider the parent subscriptions (3)Idioms feedEnglish languageHome page and general feed Comment on this entry Comment on this entry