Graafian follicle Graaf·i·an follicle or graaf·i·an follicle (grä'fē-ən, grāf'ē-)
n.
A mature ovarian follicle in which the oocyte attains its full size and the surrounding follicular cells are permeated by one or more fluid-filled cavities. Also called secondary follicle, vesicular ovarian follicle.