mudhead n. Commonly used to refer to a {MUD} player who eats, sleeps,
   and breathes MUD. Mudheads have been known to fail their degrees, drop
   out, etc., with the consolation, however, that they made wizard level.
   When encountered in person, on a MUD, or in a chat system, all a mudhead
   will talk about is three topics: the tactic, character, or wizard that
   is supposedly always unfairly stopping him/her from becoming a wizard or
   beating a favorite MUD; why the specific game he/she has experience with
   is so much better than any other; and the MUD he or she is writing or
   going to write because his/her design ideas are so much better than in
   any existing MUD. See also {wannabee}.

   To the anthropologically literate, this term may recall the Zuni/Hopi
   legend of the mudheads or `koyemshi', mythical half-formed children of
   an unnatural union. Figures representing them act as clowns in Zuni
   sacred ceremonies. Others may recall the `High School Madness' sequence
   from the Firesign Theatre album "Don't Crush That Dwarf, Hand Me the
   Pliers", in which there is a character named "Mudhead".


Source: The Jargon File