(fandom, often derogatory) A male fan who is obsessive about a particular subject (especially, something or someone in popular entertainment media).
1988, Bart Bull, Comics, (It's in the nature of comic book fanboy obsessiveness that all of these Eras and Ages and such have been religiously chronicled; it's equally in their nature that no two fanboys can ever agree about anything about any of these Ages and Eras; everything is up for debate, eternally and in microscopic detail.)
1998, Brian Doherty, Exposure: Tales From the Dark Side, Six years and seven titles later, their company, Top Cow, is the third-biggest-grossing comic line, thanks mainly to a pair of blood-soaked, modern-day Gothics that have been a hit both with fanboys and a growing number of women.
2008-12-10, Tim Barribeau, What's so great about Macs?, Apple fanboys have always devoted equal parts of their mind to genuine reasons to praise their chosen corporation, and to blindly ignoring its faults.