Source : Webster's Revised Unabridged Dictionary (1913)

Pliocene \Pli"o*cene\, a. [Written also pleiocene.] [Gr. ? more
   + ? new, recent.] (Geol.)
   Of, pertaining to, or characterizing, the most recent
   division of the Tertiary age.

Pliocene \Pli"o*cene\, n. (Geol.)
   The Pliocene period or deposits.

Source : WordNet®

Pliocene
     n : from 13 million to 2 million years ago; growth of mountains;
         cooling of climate; more and larger mammals [syn: {Pliocene
         epoch}]