The Collaborative International Dictionary
goalpost \goalpost\, goal post \goal post\, n. (Sport) One of two posts supporting a crossbar which forms a goal[3], especially in American football; also, in football the entire structure consisting of the posts, crossbar, and two uprights. To score a goal by kicking the football, the ball must pass above the crossbar and between the vertical lines formed by the uprights.
Wiktionary
n. (context sports English) Either of the pair of vertical supports limiting the goal in various ballgame, such as soccer, rugby and American football.
Usage examples of "goal post".
On the first turn a tackle named Ted Joost, who was Randy King's roommate, bumped John Butler right into the goal post and kept on going.
Even when she'd been pregnant with her sixth kid, Tina Marie had looked like a goal post with the football fastened onto its middle with duct tape.
When raised, the bar on its upright poles looked like a football goal post.
They trotted out in a straight line and slapped the goal post before they started their drills.