"Futa on female" refers to a specific subgenre of adult entertainment or erotic fiction involving characters with both male and female genitalia, typically featuring a person with female secondary sexual characteristics (such as breasts and feminine features) and male primary sexual characteristics (such as a penis) and you can watch the example on 3dfuta. The term "futa" is short for "futanari," which originates from Japanese hentai and anime/manga culture like Futa on male.