Punch above one's weight

Meaning

Competing against someone who you are no match for.

Origin

The different classes of contestants in boxing matches are distinguish by the weight of the competing boxers - heavyweight, middleweight, lightweight, flyweight etc. The sport is regulated so that only boxers of the same weight fight each other. Someone from a lighter weight wouldn't be expected to have much chance if 'punching above his weight' against a heavier fighter.

The term is often used figuratively in situations where someone finds themselves competing outside their usual class; for example, the Irish comedian Graham Norton described that, since becoming well-known, he was able to attract better-looking partners than previously and that he was 'punching above my weight' when it comes to relationships.