buy up buy up {v. phr.} To purchase the entire stock of something. The company is trying to buy up all the available shares. Categories: add yours {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: B Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Discuss