The Collaborative International Dictionary of English v.0.48:

Koala \Ko*a"la\, n.
   A tailless furry marsupial (Phascolarctos cinereus), found
   in Australia. The female carries her young on the back of her
   neck. Called also Australian bear, koala bear, native
   bear, and native sloth. The koala lives almost all of its
   life in trees, moves sluggishly like a sloth, and eats
   eucalyptus leaves almost exclusively.
   [1913 Webster +PJC] Kob

WordNet (r) 3.0 (2006):

Phascolarctos cinereus
    n 1: sluggish tailless Australian arboreal marsupial with grey
         furry ears and coat; feeds on eucalyptus leaves and bark
         [syn: koala, koala bear, kangaroo bear, native
         bear, Phascolarctos cinereus]