adjective Pro·te·ro·zo·ic \ˌprä-tə-rə-ˈzō-ik, ˌprō-\

Definition of PROTEROZOIC

:  of, relating to, or being the eon of geologic time or the corresponding segment of rocks that includes the interval between the Archean and Phanerozoic eons, exceeds in length all of subsequent geologic time, and is marked by rocks that contain fossils indicating the first appearance of eukaryotic organisms (as algae) — see geologic time table
Proterozoic noun


Greek proteros former, earlier (from pro before) + International Scientific Vocabulary -zoic — more at for
First Known Use: 1899


Next Word in the Dictionary: protervityPrevious Word in the Dictionary: proterotypeAll Words Near: Proterozoic
July 03, 2015
interpellate Hear it
to formally question a public official
Take a 3-minute break and test your skills!
How to use a word that (literally) drives some people nuts.
Test your vocab with our fun, fast game
Ailurophobia, and 9 other unusual fears