'Archean eon' definitions:

Definition of 'Archean eon'

(from WordNet)
noun
The time from 3,800 million years to 2,500 million years ago; earth's crust formed; unicellular organisms are earliest forms of life [syn: Archean, Archean eon, Archean aeon, Archeozoic, Archaeozoic, Archeozoic eon, Archaeozoic aeon]