Anime - Japanese word for animation. In English used to mean animation produced in Japan and/or the style of animation common in Japan.
Dubbed - The original foreign-language dialogue in the film or video has been replaced with voices speaking English (or whatever language is appropriate for the country in which the show will be viewed). Of course, the word "dub" is also commonly used to mean "copy", as in "to dub a tape".
Fansub - A video which has been translated and subtitled by fans. The non-profit distribution of these videos allows fans to see series that can't otherwise be seen or bought in the West. Fansubs can be found on the internet or through the anime fan-clubs found at many colleges and universities.
Ecchi - lewd, oversexed.
Furigana - Small hiragana or katakana written above kanji to clarify how the kanji is to be read. This is usually found in children's books to aid them in reading the kanji, but can also be found in adult writing to clarify which usage of a kanji symbol is intended.
Hentai - A pervert, or material which is sexually perverse.
Hiragana - The basic Japanese syllabary or alphabet, hirigana is the first writing system Japanese children learn. In adult writing, hiragana is combined with kanji and katakana.
Kanji - Kanji is the Japanese adaptation of Chinese writing. Although each symbol can carry the meaning of an entire word, kanji are usually used more for the sound that they represent and must be combined with hiragana to make meaningful Japanese words. Since kanji have both a symbolic reading and a phonetic reading, they can be used to construct clever written puns.
Katakana - One of two Japanese "alphabets". Katakana is used for words of foreign origin, technical terms, or for emphasis.
Manga - Japanese word for comics.
OAV - Original Animation Video - Anglicized version of the term "OVA" (original video animation). Denotes animation produced for the direct-to-video market.
Otaku - In Japan otaku is a derogatory term for a "stay-at-home person"; such as someone who has an obsession with anime, manga, video games, etc. English usage of "otaku" varies, but is mostly commonly used simply to mean a serious anime/manga fan.
OVA - Original Video Animation. An OVA is an anime that was produced specifically for sale on video (as opposed to TV release). OVA series generally have fewer episodes but higher animation quality than TV anime series.
Roomaji/Romanji - Japanese spelled out using Roman letters (i.e. the English alphabet).
Seinen - Young man. Used as a label for stories aimed at men in their teens or early twenties (generally sports, war, or adventure stories).
Sempai - A social senior in whose steps you are following, e.g. an upperclassman at school. The senior person is the "sempai" and the junior person is the "kohai". Sometimes used for boyfriend-girlfriend relationships especially if the girl is younger.
Sensei - A teacher or master of an art or discipline.
Shonen - Young boy. Also used as a label for stories intended for a young male audience.
Shoujo - Young woman. Also used as a label for stories intended for a young female audience.
Subtitled - The film or video is presented in its original language form with a written translation appearing as captions across the bottom of the screen.
Surtitles - Written translations appearing across the top of the screen.
Tankoubon - Manga in a paperback novel sized format.
Trade Paperback - A reprint of a serial work in the form of a larger collected edition. Tankoubon are an example of what would be called a Trade Paperback in the USA.