Ol•i•go•cenePronunciation: (ol'i-gō-sēn"), [key] Geol.
noting or pertaining to an epoch of the Tertiary Period, occurring from 40 to 25 million years ago. See table under geologic time.
the Oligocene Epoch or Series.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.