Definition of Move the Goalposts

What does the term "move the goalposts" mean? What is meant by the term "move the goalposts"?

The term "moving the goalposts" is used quite often in the mainstream.

The term refers to the idea of changing the rules after a game has already started.

For instance - let's say that a football team is lining up to kick a 45-yard field goal.

What if the opposing team was playing at home and what if they decided to move the goalposts ten yards back?

This would be unfair as the rules would be changing during a game.

The term is used in the mainstream media as well and refers to whenever somebody attempts to change the rules to their benefit after a contest has already started.

For instance - there is an election in a small African nation.

The current leader is facing a close race and decides to exclude all votes from people under the age of 30, as the majority of these people are voting for the current leader's opponent.

This would be an example of "moving the goalposts", as the rules would be changing in the middle of the election.