This phrase is used in football to describe the action of a quarterback moving outside the pocket in order to throw the ball. On most passing plays in the game of football, the quarterback is protected from the defense by his offensive line and other blockers surrounding him. This area of protected space is known as the pocket. A quarterback may move out of the pocket on a designed play, to get away from a defender, or to get a better view of receivers down the field. By moving outside the pocket, the quarterback increases his risk of getting sacked or tackled but also creates more space to throw the ball.
If the quarterback moves outside the pocket on a designed play, there may actually be blockers pulling to protect him. Even if the quarterback leaves the pocket for another reason, offensive lineman will often still attempt to block defenders from reaching him. A quarterback capable of moving outside the pocket and completing passes is considered a valuable resource since it is a very difficult skill to master.