Miocene
adjective
Mio·cene ˈmī-ə-ˌsēn 
: of, relating to, or being an epoch of the Tertiary between the Pliocene and the Oligocene or the corresponding series of rocks see Geologic Time Table
Miocene noun
Word History
Etymology
mio- (from Greek meiōn less) + -cene — more at meiosis
First Known Use
1831, in the meaning defined above