Title: MUD
Content:  A MUD (originally multi-user dungeon, with later variants multi-user dimension and multi-user domain) is a multiplayer real-time virtual world, usually text-based. MUDs combine elements of role-playing games, hack and slash, player versus player, interactive fiction, and online chat. Players can read or view descriptions of rooms, objects, other players, non-player characters, and actions performed in the virtual world. Players typically interact with each other and the world by typing commands that resemble a natural language. Traditional MUDs implement a role-playing video game set in a fantasy world populated by fictional races and monsters, with players choosing classes in order to gain specific skills 
Title: MUD
Content:  While there have been many variations in overall focus, gameplay and features in MUDs, some distinct sub-groups have formed that can be used to help categorize different game mechanics, game genres and non-game uses.
Title: MUD
Content:  Roleplaying MUDs, generally abbreviated as RP MUDs, encourage or enforce that players act out the role of their playing characters at all times. Some RP MUDs provide an immersive gaming environment, while others only provide a virtual world with no game elements. MUDs where roleplay is enforced and the game world is heavily computer-modeled are sometimes known as roleplay intensive MUDs, or RPIMUDs. In many cases, role-playing MUDs attempt to differentiate themselves from hack and slash types, by dropping the "MUD" name entirely, and instead using MUX (Multi-User Experience) or MUSH (Multi-User Shared Hallucination).
Title: Text-based game
Content:  An MUD (originally Multi-User Dungeon, with later variants Multi-User Dimension and Multi-User Domain), is a multi-user real-time online virtual world. Most MUDs are represented entirely in text, but graphical MUDs are not unknown. MUDs combine elements of role-playing games, hack and slash, interactive fiction, and online chat. Players can read or view depictions of rooms, objects, other players, non-player characters, and actions performed in the virtual world. Players typically interact with each other and the world by typing commands that resemble a natural language.
Title: MUD
Content:  powers. The objective of this sort of game is to slay monsters, explore a fantasy world, complete quests, go on adventures, create a story by roleplaying, and advance the created character. Many MUDs were fashioned around the dice-rolling rules of the Dungeons & Dragons series of games. Such fantasy settings for MUDs are common, while many others have science fiction settings or are based on popular books, movies, animations, periods of history, worlds populated by anthropomorphic animals, and so on. Not all MUDs are games; some are designed for educational purposes, while others are purely chat environments, and the flexible nature of many 
Title: MUD1
Content:   Multi-User Dungeon, or MUD (referred to as MUD1, to distinguish it from its successor, MUD2, and the MUD genre in general), is the first MUD and the oldest virtual world in existence.
Title: MUD
Content:  As a noun, the word MUD is variously written MUD, Mud, and mud, depending on speaker and context. It is also used as a verb, with to mud meaning to play or interact with a MUD and mudding referring to the act of doing so. A mudder is, naturally, one who MUDs. Compound words and portmanteaux such as mudlist, mudsex, and mudflation are also regularly coined. Puns on the "wet dirt" meaning of "mud" are endemic, as with, for example, the names of the ROM (Rivers of MUD), MUCK, MUSH, and CoffeeMUD codebases and the MUD Muddy Waters.
Title: MUD1
Content:  MUD was created in 1978 by Roy Trubshaw and Richard Bartle at the University of Essex on a DEC PDP-10. Trubshaw named the game Multi-User Dungeon, in tribute to the Dungeon variant of Zork, which Trubshaw had greatly enjoyed playing. Zork in turn was inspired by an older text-adventure game known as Colossal Cave Adventure or ADVENT. MUD1 was written in the domain-specific programming language Multi User Dungeon Definition Language (MUDDL). Its first version was written by Richard Bartle and Roy Trubshaw in BCPL. It was later ported to C++ and used in other MUDs such as MIST. In 1980, Roy Trubshaw created MUD version 3 in BCPL (the predecessor of C), to conserve memory and make the 
Title: Online game
Content:  MUD are a class of multi-user real-time virtual worlds, usually but not exclusively text-based, with a history extending back to the creation of MUD1 by Richard Bartle in 1978. MUD were the direct predecessors of MMORPG.
Title: MUD
Content:  Perhaps the most common approach to game design in MUDs is to loosely emulate the structure of a Dungeons & Dragons campaign focused more on fighting and advancement than role-playing. When these MUDs restrict player-killing in favor of player versus environment conflict and questing, they are labeled hack and slash MUDs. This may be considered particularly appropriate since, due to the room-based nature of traditional MUDs, ranged combat is typically difficult to implement, resulting in most MUDs equipping characters mainly with close-combat weapons. This style of game was also historically referred to within the MUD genre as "adventure games", but video gaming as a whole has developed a meaning of "adventure game" that is greatly at odds with this usage.

Question: What genre is MUD?
Answer: massively multiplayer online role-playing game.
MMORPG.
MMO.
RPG.
mmorpg.