Nomic is a metagame in which players can modify the rules as part of gameplay.
noun The exploitation of the rules etc. of some other game, at a higher level than simply playing the game normally; a game outside or peripheral to the actual gameplay.
noun The conventions of a gaming community; the characters, weapons, techniques, etc, which are currently considered most viable in multiplayer gameplay, and the best practices for using them.
verb Of a roleplayer, to make use of knowledge while roleplaying that they learned out of character, which their character does not know; often considered a form of cheating.