ecchi
Ecchi (or Etchi) is derived from the Japanese prononciation of the letter "H", short for hentai, and can refer to a pervert when used as a noun or sexual intercourse when used as a verb. Most often, however, it's used as a noun-adjective, and means "lewd, dirty-minded".
Note: Don't use this as a tag. We already have a rating system for obscenity. See rating:explicit instead.