The Collaborative International Dictionary of English v.0.48:

Mundane \Mun"dane\, a. [L. mundanus, fr. mundus the world, an
   implement, toilet adornments, or dress; cf. mundus, a.,
   clean, neat, Skr. ma[.n][dsdot] to adorn, dress,
   ma[.n][dsdot]a adornment. Cf. Monde, Mound in heraldry.]
   1. Of or pertaining to the world; worldly, as contrasted with
      heavenly; earthly; terrestrial; as, the mundane sphere;
      mundane concerns. -- Mun"dane*ly, adv.
      [1913 Webster]

            The defilement of mundane passions.   --I. Taylor.
      [1913 Webster]

   2. Commonplace; ordinary; banal.
      [PJC]

WordNet (r) 3.0 (2006):

mundane
    adj 1: found in the ordinary course of events; "a placid
           everyday scene"; "it was a routine day"; "there's nothing
           quite like a real...train conductor to add color to a
           quotidian commute"- Anita Diamant [syn: everyday,
           mundane, quotidian, routine, unremarkable,
           workaday]
    2: concerned with the world or worldly matters; "mundane
       affairs"; "he developed an immense terrestrial practicality"
       [syn: mundane, terrestrial]
    3: belonging to this earth or world; not ideal or heavenly; "not
       a fairy palace; yet a mundane wonder of unimagined kind"; "so
       terrene a being as himself" [syn: mundane, terrene]

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "mundane":
   Philistine, animal, arid, banausic, barren, carnal, carnal-minded,
   common, commonplace, dry, dull, earthbound, earthly, earthy,
   everyday, flat, fleshly, humdrum, infecund, infertile, insipid,
   literal, lowly, material, materialistic, matter-of-fact, nonsacred,
   ordinary, pedestrian, plain, poetryless, profane, prosaic, prosing,
   prosy, reprobate, secular, sensual, staid, stolid, stuffy,
   tellurian, telluric, temporal, terrene, terrestrial, tiresome,
   unblessed, unembellished, unfanciful, unhallowed, unholy, unideal,
   unidealistic, unimaginative, unimpassioned, uninspired,
   uninventive, unoriginal, unpoetic, unregenerate, unromantic,
   unromanticized, unsacred, unsanctified, unspiritual, vapid,
   workaday, workday, worldly



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

mundane
 n.

    [from SF fandom]

    1. A person who is not in science fiction fandom.

    2. A person who is not in the computer industry. In this sense, most often
    an adjectival modifier as in ?in my mundane life....? See also Real World
    , muggle.


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

mundane

    Someone outside some group that is implicit from the
   context, such as the computer industry or science fiction
   fandom.  The implication is that those in the group are
   special and those outside are just ordinary.

   (2000-07-22)