An pathetic insult used by people who can't think of anything better to say and are very bad at grammar and say "your" instead of "you're" when appropriate.
Bob: Hey dude what's happening?
Chris: Fuck off
Bob: What have I done?!
Chris: Your gay!
Bob: Shut the hell up you retarded fuckfaced pussy unclefucking douchebag turd burglar!!!
Chris: Um... your gay.