(used interjectionally to call attention to an impending danger or the need for immediate alertness).
Pronunciation: (hedz'up"), [key]
quick to grasp a situation and take advantage of opportunities; alert; resourceful.
Chiefly Politics.a warning: sending a heads-up to the Pentagon about possible attacks.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.