Proterozoic: Meaning and Definition of

Prot•er•o•zo•ic

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. See table under