Meaning of heads up

heads' up'

Pronunciation: [key]
  1. (used interjectionally to call attention to an impending danger or the need for immediate alertness).

heads-up

Pronunciation: (hedz'up"), [key]
— adj.
  1. quick to grasp a situation and take advantage of opportunities; alert; resourceful.
—n.
  1. a warning: sending a heads-up to the Pentagon about possible attacks.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.
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