from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Of or belonging to the earlier of the two divisions of Precambrian time, from approximately 3.8 to 2.5 billion years ago, marked by an atmosphere with little free oxygen, the formation of the first rocks and oceans, and the development of unicellular life. See Table at geologic time.
- adj. Of or relating to the oldest known rocks, those of the Precambrian Eon, that are predominantly igneous in composition.
- n. The Archean Eon. Also called Archeozoic.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- adj. of or relating to the earliest known rocks formed during the Precambrian Eon
- n. the time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life
From Greek arkhaios, ancient; see archaic.(American Heritage® Dictionary of the English Language, Fourth Edition)