A boy or man who is ardently devoted to a single hobby or interest.
A man or boy who is a devoted fan, as of comic books, science fiction, or certain types of computer technology.
A male, or "fangirl" if female, who is devoted to a particular product or company. Fanboys are loyal and steadfast in their dedication and opinions. With regard to technology, fanboys outnumber fangirls by a huge margin and may be enamored with specific computer platforms, MP3 players, smartphones, operating systems, video games or applications. See iSheep, Fandroid and fanboi.