heads-up

A warning or call to pay attention; an advisory notice; a notice of what is to happen; a holler.

“Send everyone a heads-up about the inspection tomorrow.”

Involving two players. (usually said when there are only two players in the table; or, when all players except two folded)

“There are seven players on the table. Five folded, the remaining two played heads-up until the showdown.”

With head directly above the neck, eyes front.

“A heads-up posture meant the pilot couldn't pay attention to his instruments.”

Alert; vigilant

“Getting those marbles off the red carpet was a real heads-up move.”