MMO

MMO stands for Massively Multiplayer Online game.

MMORPG - Massively Multiplayer Online Role Playing Game: A game type in which many individual client systems running the game connect to a centralized server which renders a world. Gameplay is otherwise similar to a traditional RPG in which a player slowly gains both experience and power by overcoming obstacles which, in turn, allow larger and more difficult obstacles to be attempted.
 * MMO - wikipedia entry
 * MMORPG - wikipedia entry