- of, relating to, or denoting the eon that constitutes the earlier (or middle) part of the Precambrian, in which there was no life on earth. It precedes the Proterozoic eon. Also called azoic.
The Archean extended from the origin of the earth (see Precambrian) to about 2,500 million years ago. In models that include the Priscoan eon, the Archean began about 4,000 million years ago
late 19th century: from Greek arkhaios 'ancient' + -an