The Collaborative International Dictionary of English v.0.48:

Uintatherium \U*in`ta*the"ri*um\, n. [NL., fr. Uinta, the Indian
   name of the region where the animals were discovered + Gr.
   qhri`on beast.] (Paleon.)
   An extinct genus of large Eocene ungulates allied to
   Dinoceras. This name is sometimes used for nearly all the
   known species of the group. See Dinoceras.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Dinoceras \Di*noc"e*ras\, n. [NL., fr. Gr. ? terrible + ?, ?,
   horn.] (Paleon.)
   A genus of large extinct Eocene mammals from Wyoming; --
   called also Uintatherium. See Illustration in Appendix.
   [1913 Webster]

   Note: They were herbivorous, and remarkable for three pairs
         of hornlike protuberances on the skull. The males were
         armed with a pair of powerful canine tusks.
         [1913 Webster]

WordNet (r) 3.0 (2006):

Uintatherium
    n 1: type genus of the Uintatheriidae; extinct large herbivorous
         ungulates somewhat resembling elephants; from the Eocene in
         Wyoming [syn: Uintatherium, genus Uintatherium]