Neoproterozoic Definition

nēō-prŏtər-ə-zōĭk, -prōtər-
adjective
Of, relating to, or being the most recent of the three eras of the Proterozoic Eon, from approximately 1.0 billion to 542 million years ago, marked by the formation of extensive glaciers reaching as far south as the equator and the first appearance of multicellular life.
American Heritage
noun
The Neoproterozoic Era.
American Heritage