A wombat is a small mammal somewhat like a
kangaroo.
To quote
Ogden Nash,
'The wombat lives across the seas
Among the far Antipodes.
He may subsist on nuts and berries
Or, then again, on missionaries.
I, for one, would not engage the wombat
in any form of mortal combat.'
The
Jargon File mentions wombats too. . . it stands for Waste of
Money,
Brains, and
Time, for example, "Running any
Microsoft program for
Unix is a total wombat."