round out . round out {v. phr.} To complete; make whole. He needs only one or two more rare compact discs to round out his collection of Vivaldi. Categories: add yours add yours {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: R Subscribe to: American Idioms► Also consider the parent subscriptions (3)Idioms feedEnglish languageHome page and general feed Discuss Discuss