(Australian rules football) One of a pair of shorter outer posts at either end of the field; a ball kicked between a behind post and a goal post scores one point.

plural of behind post

(slang) In a prison camp or refugee camp. / (by extension, slang) In prison.

(American football) At the quarterback position.

The person using a firearm; the shooter.

(idiomatic) In private; in one's private life; lacking (normal) public disclosure, in camera. / (idiomatic, sports) Without public spectators.

(idiomatic) In a difficult situation or tight spot; at a disadvantage.

(idiomatic) Without somebody's knowledge; secretly.

(idiomatic) Inexperienced; just beginning; immature (especially in judgment).

(sports) To be in a winning position after having been in a losing position.