heads-up . heads-up {adj.}, {informal} Wide-awake; alert; watchful; intelligent. You must play hard, heads-up baseball to win this game. Compare: ON ONE'S TOES, ON THE BALL. Categories: add yours {adj.} {informal} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: H Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Leave my opinion