Proterozoic

//ˌpɹoʊt(ə)ɹrəˈzoʊɪk// adj, name

adj, name ·Uncommon ·Advanced level

Definitions

Adjective
  1. 1
    Of or relating to the geologic eon from 2,500 Ma to 541.0±1.0 Ma. not-comparable
  2. 2
    Alternative form of Proterozoic. alt-of, alternative, not-comparable
Adjective
  1. 1
    formed in the later of two divisions of the Precambrian era wordnet
Proper Noun
  1. 1
    The eon from 2,500 Ma to 541.0±1.0 Ma, the beginning of the Phanerozoic, marked by the build up of oxygen in the atmosphere and the emergence of primitive multicellular life.

Synonyms

All synonyms
archaeanearlyperiodproterozoic aeonproterozoic eontime

Example

More examples

"Then about 2.3 to 2.5 billion years ago, during the Proterozoic Eon, blue-green algae called cyanobacteria, living in Earth’s shallow oceans, began emitting enough oxygen through photosynthesis to create the permanently oxygenated atmosphere that keeps us alive today."

Etymology

From protero- + -zoic.

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.