The Collaborative International Dictionary of English v.0.48:

Rhinoceros \Rhi*noc"e*ros\ (r[-i]*n[o^]s"[-e]*r[o^]s), n. [L.,
   fr. Gr. "rinoke`rws, "rinoke`rwtos; "ri`s, "rino`s, the nose
   + ke`ras a horn: cf. F. rhinoc['e]ros. See Horn.] (Zool.)
   Any pachyderm belonging to the genera Rhinoceros,
   Atelodus, and several allied genera of the family
   Rhinocerotidae, of which several living, and many extinct,
   species are known. They are large and powerful, and usually
   have either one or two stout conical median horns on the
   snout.
   [1913 Webster]

   Note: The Indian, or white, and the Javan rhinoceroses
         (Rhinoceros Indicus and Rhinoceros Sondaicus) have
         incisor and canine teeth, but only one horn, and the
         very thick skin forms shieldlike folds. The two or
         three African species belong to Atelodus, and have
         two horns, but lack the dermal folds, and the incisor
         and canine teeth. The two Malay, or East Indian,
         two-horned species belong to Ceratohinus, in which
         incisor and canine teeth are present. See Borele, and
         Keitloa.
         [1913 Webster]

   Rhinoceros auk (Zool.), an auk of the North Pacific
      (Cerorhina monocrata) which has a deciduous horn on top
      of the bill.

   Rhinoceros beetle (Zool.), a very large beetle of the genus
      Dynastes, having a horn on the head.

   Rhinoceros bird. (Zool.)
   (a) A large hornbill (Buceros rhinoceros), native of the
       East Indies. It has a large hollow hornlike process on
       the bill. Called also rhinoceros hornbill. See
       Hornbill.
   (b) An African beefeater (Buphaga Africana). It alights on
       the back of the rhinoceros in search of parasitic
       insects.
       [1913 Webster]

WordNet (r) 3.0 (2006):

rhinoceros beetle
    n 1: any of various large chiefly tropical beetles having horns
         on the head; pest on coconuts