Pronunciation: (mī'u-sēn"), [key] Geol.
noting or pertaining to an epoch of the Tertiary Period, occurring from 25 to 10 million years ago, when grazing mammals became widespread. See table under geologic time.
the Miocene Epoch or Series.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.