A goalpost is one of the two tall vertical posts that mark the edges of a goal in sports like soccer, football, and rugby. Together with the crossbar connecting them at the top, the goalposts define the area where you need to get the ball to score. In soccer, you're trying to kick the ball between the goalposts and under the crossbar. In American football, the kicker aims to send the ball between the goalposts and above the crossbar for a field goal.

The word also appears in a common phrase: moving the goalposts. This means changing the rules or requirements after someone has already started working toward a goal, making success harder or impossible to achieve. Imagine practicing free throws all week for a basketball contest, then arriving to find the hoop has been raised three feet higher. That's what it feels like when someone moves the goalposts. A teacher who keeps adding new requirements to an assignment after you've already started is moving the goalposts. So is a friend who changes what counts as “winning” a game once they start losing.