Another term for these servers is the Tiny family.
The asterisk is often used in computer programming languages to represent a wildcard (any number of arbitrary characters), which suggests a usage that encompasses MUDs in general. However, confusingly, MU* is often used in a manner exclusive of services specifically described as MUDs, with the MU* term meant to distance the TinyMUD family of "social MUDs" from "combat-oriented" MUDs. With the dominant usage of MUD being as a generic term rather than specifically denoting combat-oriented games — indeed, both TinyMUD and MOO are MUDs in name (MOO stands for MUD, Object-Oriented), while MUSH and MUCK are backronymed puns on "MUD" — this positions MU* as actually being a subset of MUD.
- Bartle, Richard (2003). Designing Virtual Worlds. New Riders. p. 3. ISBN 0-13-101816-7. "Confusingly, although the term MUD applies to virtual worlds in general, the term MU* does not—it's used strictly for text-based worlds."
- Bartle, Richard (2003). Designing Virtual Worlds. New Riders. pp. 9–10. ISBN 0-13-101816-7. "TinyMUD was deliberately intended to be distanced from the prevailing hack-and-slay AberMUD style, and the "D" in its name was said to stand for "Dimension" (or, occasionally, "Domain") rather than "Dungeon;" this is the ultimate cause of the MUD/MU* distinction that was to arise some years later."
- Hahn, Harley (1996). The Internet Complete Reference (2nd ed.). Osborne McGraw-Hill. p. 553. ISBN 0-07-882138-X. "[...] for example, MUCK, MUSH, MUSE, MAGE, MUG, MOO, and so on. All of these things are muds [...] For instance, you may read that MUSH stands for "Multi-User Shared Hallucination". My advice is to forget the acronyms. Consider all of these strange things to be types of muds and leave it at that."