archeozoic 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 s of or belonging to earlier of two divisions of the Precambrian era archeozoic life forms Synonym(s) Archean Archean eon Archean aeon Archeozoic Archaeozoic Archeozoic eon Archaeozoic aeon archaeozoic