Return the Flirt
When you flirt with someone, even if you are not attracted to them, just because they flirted first. Can be done consciously or unconsciously. Can be done by men or women. Can even be done by a heterosexual when he/she is flirted with by a homosexual.
Guy 1: What were you doing flirting with that girl?! She's and ugly ass bitch! and you have a girlfriend! I know she has a thing for you but still man

Guy 2: Wait What? I didn't even realize. I must have just been a return the flirt instance.