I. | ̷ ̷ ̷ ̷ ̷ ̷|zōik adjective
Usage: usually capitalized
Etymology: International Scientific Vocabulary proter- + -zoic
: of or relating to a grand division of geological history that includes the entire interval from the beginning of the Huronian to the close of the Keweenawan, perhaps exceeds in length all of subsequent geological time, and is marked by rocks that contain a few fossils indicating the existence of animals as highly organized as annelid worms and of blue-green and brown algae — see geologic time table
II. noun
( -s )
Usage: usually capitalized
: the Proterozoic era or system of rocks