In multiplayer online games, a MUSH (a backronymed[1] variation on MUD most often expanded as Multi-User Shared Hallucination,[2][3][4] though Multi-User Shared Hack,[5] Habitat, and Holodeck are also observed) is a text-based online social medium to which multiple users are connected at the same time.
[7][8] A primary feature of MUSH codebases that tends to distinguish it from other multi-user environments is the ability, by default, of any player to extend the world by creating new rooms or objects and specifying their behavior in the MUSH's internal scripting language.
[11][12][13][14][15] There is nothing in the code base that restricts a new MUSH from being a traditional hack-and-slash MUD-style game.
[16] However, the earliest uses of MUSH servers were for roleplaying and socializing, and these early trends have largely governed their descendants.
[16] All MUSH servers provide a flag that, when set on a player, bestows the ability to view and modify nearly everything in the game's database.