ˌheads-ˈup noun [singular] informal
a warning that something may happen:
Here's a heads-up for investors in real-estate stocks.

[TahlilGaran] Dictionary of Contemporary English ▲

heads up
look up because something may hit you.
Usage notes: often shouted as a warning:
Heads up! Watch out for the baseball!

[TahlilGaran] English Idioms Dictionary ▲

Heads up!
Raise your head and be careful about some nearby danger!
"Heads up," the construction worker yelled at the other worker.

[TahlilGaran] English Idioms Dictionary ▲

heads up(1)
interj., informal Keep your head up and be careful or ready.
■ Used as a warning to prepare for something or clear the way
"Heads up!" said the waiter carrying the hot food.
Heads up, boys! A train is coming.
Heads up, now! You can do better than that.
Synonym: LOOK ALIVE, LOOK OUT.

[TahlilGaran] English Idioms Dictionary ▲

heads-up(2)
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.

[TahlilGaran] English Idioms Dictionary ▲