1) Adult anime 2) Anime with adult themes 1) Smut 
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...
(hen-tai) Hentai means "pervert" or "perversion" in Japanese. It is usually associated with erotic or sexually-explicit anime.
Japanese word for 'pervert' or 'perverted'. In the west it is used a generic term to describe pornographic anime and manga. Pronounced ‘hen-tie`.
Japanese word meaning `perverted”; in anime, it refers to pornographic material
Japanese for 'pervert', refers to pornographic material.
A Japanese slang word meaning perverted or perversion. In the world of manga and anime, hentai refers to the adult oriented titles that present extreme, graphic sexual imagery. A common Western stereotype concerning manga and anime is that these artforms are filled with graphic sex. While such imagery exists (and has always existed in Japan), henta...
Japanese for "pervert." Hentai is an actual genre of anime that includes major nudity and sexual situations. More info on Hentai
Literally translating as 
Anime or manga with a focus on lesbian relationships. In Japan, the term denotes a broad spectrum of attraction between women. It is also used for sexually explicit content outside Japan,
Pervert. Abnormal. Ecchi