I. ˈēəˌsēn adjective
Usage: usually capitalized
Etymology: eo- + -cene
: of or relating to the second principal subdivision of the Tertiary — used commonly of the epoch following the Paleocene and preceding the Oligocene but sometimes of all the Cenozoic era preceding the Miocene; see geologic time table
II. noun
( -s )
Usage: usually capitalized
1. : the Eocene epoch
2. : the series deposited during the Eocene epoch