The Collaborative International Dictionary of English v.0.48:

Marsupial \Mar*su"pi*al\ (m[aum]r*s[=u]"p[i^]*al), a. [Cf. F.
   marsupial.]
   [1913 Webster]
   1. (Zool.) Having a pouch for carrying the immature young; of
      or pertaining to the Marsupialia.
      [1913 Webster]

   2. (Anat. & Zool.) Of or pertaining to a marsupium; as, the
      marsupial bones.
      [1913 Webster]

   Marsupial frog. (Zool.) See Nototrema.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

marsupial \mar*su"pi*al\, n. (Zool.)
   One of the Marsupialia.
   [1913 Webster]

WordNet (r) 3.0 (2006):

marsupial
    adj 1: of or relating to the marsupials; "marsupial animals"
    n 1: mammals of which the females have a pouch (the marsupium)
         containing the teats where the young are fed and carried
         [syn: marsupial, pouched mammal]

Moby Thesaurus II by Grady Ward, 1.0:

37 Moby Thesaurus words for "marsupial":
   amphibian, aquatic, biped, camerated, canine, cannibal, capsular,
   carnivore, cellular, cetacean, chordate, cosmopolite, cystic,
   feline, gnawer, herbivore, insectivore, invertebrate, locular,
   mammal, mammalian, marsupialian, omnivore, primate, quadruped,
   reptile, rodent, ruminant, saccular, scavenger, siliquose,
   ungulate, varmint, vascular, vermin, vertebrate, vesicular