[ ˌprəʊt(ə)rə'zəʊɪk ]
■ adjective Geology relating to or denoting the later part of the Precambrian aeon (between the Archaean aeon and the Cambrian period, about 2,500 to 570 million years ago), in which the earliest forms of life evolved.
Origin
C19: from Gk proteros 'former' + zōē 'life', zōos 'living' + -ic .