Primary oocyte. Definition. noun, plural: primary oocytes. The oocyte that arises from the oogonium via the process of oocytogenesis, and gives rise to secondary oocyte and polar body after first meiotic division (meiosis I).Supplement. In humans, the primary oocytes are produced by the process of oocytogenesis that occurs during embryonic stage.At that time each oogonium inside the ovaries of the fetus divides and enters the initial stage of meiosis I to become the primary oocyte.upplement. In humans, the primary oocytes are produced by the process of oocytogenesis that occurs during embryonic stage. At that time each oogonium inside the ovaries of the fetus divides and enters the initial stage of meiosis I to become the primary oocyte.