What is "mercy rule"

n. (context sports English) In sporting parlance, a rule that ends a one-sided contest prior to its natural conclusion.

A mercy rule—also known by the terms slaughter rule, knockout rule and skunk rule—brings a sports event to an early end when one team has a very large and presumably insurmountable lead over the other team. It is called the mercy rule because it spares the losing team the humiliation of suffering a loss by an even larger number of points, and denies the winning team the satisfaction thereof, and prevents running up the score, a generally discouraged practice in which the opponent continues to score beyond the point when the game has become out of hand. The mercy rule is most common in North America and primarily in North American sports such as baseball or softball, where there is no game clock and play could theoretically continue forever, although it is also used in sports such as ice hockey and American football.