A meta breaking glitch of a video game is a glitch that when discovered significantly breaks the meta.
In non-video game-game, it does sometimes happen that a meta is broken as well, but these events tend to be rarer and less dramatic than meta-breaking due to computer program glitches.
In PvP games, those glitches are generally forbidden by existing rules, and quickly patched after discovered.
In speedrunning however, they are either incorporated in the existing strategy, or may lead to the creation of a new run category for particularly significant glitches.