Pronunciation: (är"kē-u-zō'ik), [key] Geol.
noting or pertaining to the earlier half of the Precambrian Era, from about 5 billion to 2.5 billion years ago, during which the earliest datable rocks were formed and from which the oldest known fossil forms, blue-green algae and bacteria, have been recovered. See table under geologic time.
the Archeozoic division of geologic time or the rock systems formed then. Also,Archaeozoic.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.