A massively single-player online game or a MSO, is a new term coined by Will Wright to refer to a game that uses player-made content, but all content is controlled by the game itself, in a manner that prevents any direct interaction. This gaming environment is designed to prevent problems that occur in Massively multiplayer online games, such as excessive competition, "ganging up" on new players, and gameplay that would be boring due to the game being too easy or difficult.
Origin The term "massively single-player online game" was a term coined by Will Wright to describe the form of play in his upcoming Spore, which did not seem to fit the criteria for any other category.