The Collaborative International Dictionary of English v.0.48:

Phalanger \Pha*lan"ger\, n. [Cf. F. phalanger. See Phalanx.]
   (Zool.)
   Any marsupial belonging to Phalangista, Cuscus,
   Petaurus, and other genera of the family
   Phalangistid[ae]. They are arboreal, and the species of
   Petaurus are furnished with lateral parachutes. See Flying
   phalanger, under Flying.
   [1913 Webster]

WordNet (r) 3.0 (2006):

phalanger
    n 1: small furry Australian arboreal marsupials having long
         usually prehensile tails [syn: phalanger, opossum,
         possum]