WordNet (r) 3.0 (2006):

Australia
    n 1: a nation occupying the whole of the Australian continent;
         Aboriginal tribes are thought to have migrated from
         southeastern Asia 20,000 years ago; first Europeans were
         British convicts sent there as a penal colony [syn:
         Australia, Commonwealth of Australia]
    2: the smallest continent; between the South Pacific and the
       Indian Ocean

The Devil's Dictionary (1881-1906):

AUSTRALIA, n.  A country lying in the South Sea, whose industrial and
commercial development has been unspeakably retarded by an unfortunate
dispute among geographers as to whether it is a continent or an
island.