Definition of: Pleistocene

(plīs′tə·sēn) Geol. noun
1. The epoch following the Pliocene; the first of the two epochs of the Quaternary period, characterized by ice sheets over much of the northern hemisphere; the glacial epoch of northern Asia, Europe, and North America.
2. The rock series of this period.
—adjective Pertaining to this epoch or to its rock series. [<Gk. pleistos most + kainos new]