Best definition
A Person (Usually Male) who plays the XBOX as a Hobby or in a more pathetic case an important part of their daily lifestyle.
Also usually a question you ask a fellow nerd.
“Hey! Are you a XBOXer?”
XBOXer: define #2
A white boy who only plays xbox and denounces any other gaming company, only cares about the “graphx”.
White Boy: Nintendo and Sony fucking suck, Xbox has such better graphics!!!

Me: oh my god that’s not even true you stupid Xboxer! Have you seen the PS4??!!