[sometimesp-] designating or of the geologic eon characterized by the development of sedimentary rock, shallow seas, and the first soft-bodied marine invertebrates; Precambrian, esp. late Precambrian
Origin of Proterozoicfrom Classical Greek proteros, former, comparative of pro, forward (see pro-) + zo- + -ic
the Proterozoic Eon or its rocks
Of, relating to, or being the most recent of the two divisions of Precambrian time, from about 2.5 billion to 542 million years ago, marked by the formation of stable continents, the buildup of oxygen, and the appearance of the first multicellular eukaryotic life forms. geologic time
The Proterozoic Eon.
Origin of ProterozoicGreek proteros earlier, former ; see per1 in Indo-European roots. -zoic