In Japanese, the term describes any type of perverse or bizarre sexual desire or act; it does not represent a genre of work. Internationally, hentai is a catch-all term to describe a genre of anime and manga pornography. English adopts and uses hentai as a genre of pornography by the commercial sale and marketing of explicit works under this label.
Hentai's narrow Japanese usage and broad international usage are often incompatible. Weather Report Girl is considered yuri hentai in English usage for its depiction of lesbian sex, but in Japan it is just yuri. The definition clash also appears with the English definition of yuri as any lesbian relationship, as opposed to its sexually explicit definition in Japan.(Full article...)