Etchi
Japanese pronunciation of the letter "H", the first letter of the word "hentai" (and is often written as such). 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").
In English, the word is often used in the context of manga and anime. However, "ecchi" has historically often been used as a synonym of "hentai", presumably due to confusion of the two; thus it can carry different connotations than allowed for by the original Japanese. In recent years, however, its use by English-speakers has largely realigned with the Japanese meaning -- although "H" (pronounced as the standard "aitch") has become a completely separate term, inclusive of all of the above.
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.
