The Collaborative International Dictionary of English v.0.48:

outback \outback\ n.
   The remote bush country of Australia; as, they hunted
   kangaroo in the outback. [Australian]
   [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

outback \outback\ adj.
   same as out-of-the-way. [prenominal]

   Syn: backwoods(prenominal), out-of-the-way, remote.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

outback
    adj 1: inaccessible and sparsely populated; [syn: outback(a),
           remote]
    n 1: the bush country of the interior of Australia