Phanerozoic eon pha·ne·ro·zoiceon uncommon noun 1. the period from about 5,400 million years ago until the present SynonymsPhanerozoicPhanerozoic eonPhanerozoic aeon Related words Broader terms eon Part of Cenozoic WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
