The Jargon File (version 4.4.7, 29 Dec 2003):

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?.


The Free On-line Dictionary of Computing (30 December 2018):

mudhead

    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
   favourite 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.

   [Jargon File]

   (1994-11-29)