- Eocene⇄adj. of or having to do with these epochs or their rocks.
- Eocene⇄Eocene, noun, adjective.
- Eocene⇄noun 1. the second epoch of the Tertiary period of the Cenozoic era, after the Paleocene and before the Oligocene, when the lowest rocks and the ancestors of many modern mammals appeared.
2. the earliest epoch of the Tertiary period, now more comm