[prot-er-uh-zoh-ik, proh-ter-]Geology
  1. noting or pertaining to the latter half of the Precambrian Era, from about 2.5 billion to 570 million years ago, characterized by the appearance of bacteria and marine algae; Algonkian.
  1. the Proterozoic division of geologic time or the rock systems formed then; Algonkian.

Origin of Proterozoic

First recorded in 1905–10; protero- + zo- + -ic Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for proterozoic

Historical Examples of proterozoic

  • Similar forms are abundant in late Proterozoic strata of Montana.


    William J. Miller

  • But how may we separate the Proterozoic rocks from the Archeozoic?


    William J. Miller

  • This second series of rocks is called the Proterozoic (beginning of life) series, and marks a long age in the worlds history.

  • Proterozoic , the age of invertebrate dominance, containing an early and a late ice age.


    Allen Chaffee

  • Proterozoic fossils have been found in places where the present average temperature approaches 0°C.

    Climatic Changes

    Ellsworth Huntington

British Dictionary definitions for proterozoic


  1. the later of two divisions of the Precambrian era, during which the earliest plants and animals are assumed to have livedCompare Archaeozoic
  1. of or formed in the late Precambrian era
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for proterozoic



1880, from protero- + zoic.

Online Etymology Dictionary, © 2010 Douglas Harper

proterozoic in Science


  1. The later of the two divisions of the Precambrian Eon, from about 2.5 billion to 540 million years ago. The Proterozoic was characterized by the formation of stable continents, the appearance of abundant bacteria and archaea, and the buildup of oxygen in the atmosphere. By about 1.8 billion years ago the oxygen buildup was significant enough to cause many types of bacteria to die out. At this time eukaryotes, including multicellular algae and the first animals, first appear in the fossil record. See Chart at geologic time.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.