What is "cumulus oophorus"

The cumulus oophorus (Latin cumulus=heap, Greek oo=egg + phor=carrier; Latinized ending "-us"), also called discus proligerus, is a cluster of cells (called cumulus cells) that surround the oocyte both in the ovarian follicle and after ovulation. In the antral follicle, it may be regarded as an extension of the membrana granulosa. The innermost layer of these cells is the corona radiata.

This layer of cells must be penetrated by spermatozoa in order for fertilization to occur.