Phanerozoic
adjective
Phan·er·o·zo·ic ˌfa-nə-rə-ˈzō-ik 
: of, relating to, or being an eon of geologic history that comprises the Paleozoic, Mesozoic, and Cenozoic or the corresponding systems of rocks see Geologic Time Table
Phanerozoic noun
Word History
Etymology
Greek phanerós "visible, conspicuous" (from phan-, base of phaínomai, phaínesthai "to become visible, come to light, appear" + -eros, adjective suffix) + -o- + -zoic entry 2 — more at fantasy entry 1
Note: The term was introduced by the American geologist George Halcott Chadwick (1876-1953) in "Subdivision of Geologic Time," Bulletin of the Geological Society of America, vol. 41 (1930), pp. 47-48. The name refers to the easily visible fossil records that appear in this eon, in contrast to the earlier period, which Chadwick referred to collectively as the Cryptozoic (see crypto-, -zoic entry 2).
First Known Use
1930, in the meaning defined above