Megagamete is a term used in biology to describe the female reproductive cell in plants. However, there are a few synonyms that can be used to describe this large gamete. The most common synonym is "ovum," which is a more general term for a female reproductive cell in animals and humans. Another term that can be used to describe the megagamete is "egg cell." Additionally, some sources also use the term "macrogamete" which literally translates to "large gamete." Regardless of the term used, the megagamete plays a crucial role in the sexual reproduction of plants and is necessary for the formation of seeds.