Dictionary.net

• The cell which becomes an ovum.

1898 - American pocket medical dictionary
By Willam Alexander Newman Dorland

• See primitive ovum, under ovum. [Lat.]

• The rudiment of a primitive ovum; a germ epithelium cell in process of development into a primitive ovum in the embryo. [Lat.]

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe