Source : Webster's Revised Unabridged Dictionary (1913)

Pleistocene \Pleis"to*cene\, a. [Gr. ? most + ? new.] (Geol.)
   Of or pertaining to the epoch, or the deposits, following the
   Tertiary, and immediately preceding man. -- n. The
   Pleistocene epoch, or deposits.

Source : WordNet®

Pleistocene
     n : from two million to 11 thousand years ago; extensive
         glaciation of the northern hemisphere; the time of human
         evolution [syn: {Pleistocene epoch}, {Glacial epoch}]