The Collaborative International Dictionary of English v.0.48:

Wombat \Wom"bat\, n. [From the native name, womback, wombach, in
   Australia.] (Zool.)
   Any one of three species of Australian burrowing marsupials
   of the genus Phascolomys, especially the common species
   (Phascolomys ursinus). They are nocturnal in their habits,
   and feed mostly on roots.
   [1913 Webster]

WordNet (r) 3.0 (2006):

wombat
    n 1: burrowing herbivorous Australian marsupials about the size
         of a badger

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

WOMBAT
 /wom'bat/, adj.

    [acronym: Waste Of Money, Brains, And Time] Applied to problems which are
    both profoundly uninteresting in themselves and unlikely to benefit
    anyone interesting even if solved. Often used in fanciful constructions
    such as wrestling with a wombat. See also crawling horror, SMOP. Also
    note the rather different usage as a metasyntactic variable in 
    Commonwealth Hackish.

    Users of the PDP-11 database program DATATRIEVE adopted the wombat as
    their notional mascot; the program's help file responded to ?HELP WOMBAT?
    with factual information about Real World wombats.


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

WOMBAT

   Waste Of Money, Brains, And Time.

   Problems which are both profoundly uninteresting in
   themselves and unlikely to benefit anyone interesting even if
   solved.  Often used in fanciful constructions such as
   "wrestling with a wombat".

   See also crawling horror, SMOP.

   [Jargon File]

   (1995-03-10)


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

wombat

   1.  A metasyntactic variable in Commonwealth
   Hackish.

   2.  wombat.doc.ic.ac.uk.

   [Jargon File]

   (1995-03-10)