RhymeZone: paleoproterozoic definitions

Definitions of Paleoproterozoic:

noun: (geology) The era from 2,500 Ma to 1,600 Ma, marked by a dramatic increase in atmospheric oxygen.
adjective: (geology) Of a geologic era within the Proterozoic eon from 2,500 to 1,600 million years ago.

(Definitions from Wiktionary)