Favorite part of my AP Biology book part IV ---> G-15 Glossary, Oogamy: (Oh-OG-um-ee) A condition in which male and female gametes differ, such that small, flagellated sperm fertilizes a large, nonmotile egg.

It's a word that starts with two O's!
See also: Oogenesis, oodles, oolite, ooze.