'proterozoic' definitions:
Definition of 'proterozoic'
(from WordNet)
adjective
Formed in the later of two divisions of the Precambrian era; "proterozoic life forms"
noun
From 2,500 to 544 million years ago; bacteria and fungi; primitive multicellular organisms [syn: Proterozoic, Proterozoic eon, Proterozoic aeon]