ˈgrä]fēən-, ˈgra] noun
Usage: sometimes capitalized G
Etymology: Regnier de Graaf died 1673 Dutch anatomist + English -ian
: a vesicle in the ovary of a mammal enclosing a developing egg and consisting in the typical form of an outer fibrous sheath and an inner cellular and vascular sheath derived from the ovarian stroma and separated by a hyaline basement membrane from an epithelial zone derived from the germinal epithelium and made up of several layers of small usually polyhedral cells that are heaped at one point into a mound which projects into the fluid-filled cavity of the vesicle and encloses the growing egg