Pro·​te·​ro·​zo·​ic ˌprä-tə-rə-ˈzō-ik How to pronounce Proterozoic (audio)
: 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 (such as algae) see Geologic Time Table
Proterozoic noun

Word History


Greek proteros former, earlier (from pro before) + -zoic entry 2 — more at for

First Known Use

1887, in the meaning defined above

Time Traveler
The first known use of Proterozoic was in 1887

Dictionary Entries Near Proterozoic

Cite this Entry

“Proterozoic.” Dictionary, Merriam-Webster, Accessed 22 Jun. 2024.

Kids Definition


: of, relating to, or being an eon of geologic time between the Archean and the Phanerozoic eons that exceeds in length all of following geologic time and is marked by rocks which contain fossils indicating the existence of algae and small soft-bodied animals resembling worms and jellyfish
also : relating to the corresponding system of rocks see geologic time
Proterozoic noun
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