转贴自Wikipedia:
In modern Japanese slang, the term otaku refers to fan of, or is specialized in any particular theme, topic, or hobby. Common uses are anime otaku (a fan of anime ) and manga otaku (a fan of Japanese comic books or manga), pasokon otaku (personal computer geeks), gēmu otaku (playing video games), and wota (pronounced 'ota', previously referred to as "idol otaku") that are extreme fans of idols, heavily promoted singing girls. There are also tetsudō otaku or denshamania (metrophiles) or gunji otaku (military geeks).
While these are the most common uses of otaku, the word can be applied to anything (music otaku, martial arts otaku, cooking otaku, etc).
