What does the term META mean in League of Legends?

The abbreviation META, which means Most Effective Tactic Available, in any MOBA (Multiplayer Online Battle Arena) game refers to the most effective combination of champions, builds, and runes used in the game during a certain patch that contains the highest winning rate. This causes pro-players and casual players to do research on what the meta is in order to adapt to the playing environment. As a result, for a certain period of time some champions are constantly being contested on the pick and ban phase of the game until the meta rotates once more.