term often used in discussing video games, especially those which are under continous develepment. Adding new features, balancing game mechanics etc. usually affects the way the game is played. "Current meta" describes actual up-to-date consent among the players how to play the game / make their choices during the gameplay. "Current meta" could be based on (un)offcial statistics taking on account many different aspects (e.g. percentage of win, favourite choices, efectivity, etc.)
"So last update will change current meta a lot, since they debuffed the 3 strongest heroes you can chose from."