Ecchi
The word ecchi is etymologically derived from the Japanese pronunciation of the letter H. In modern Japanese, the word is predominantly "sexual" in nature (akin to the English words dirty or naughty), carrying slightly negative connotations, but not necessarily "perverted" (which is usually reserved for the word hentai) unless it is being used to describe a person. Note that "ecchi" is a non-standard romanization — using Hepburn it would be "etchi", but this spelling is comparatively rare both in Japan and outside it.