Someone who knows his girlfriend is cheating on him, or at least messing around with a bunch of other guys, but chooses to ignore it because he can't resist her.
Made popular by
The Killers's song, "Mr. Brightside."
"Dude, Jeffery's girl is over there making out with some guy! Does he know about it?"
"Yeah, but he's a Mr. Brightside, so he just ignores it."
Buy a
Mr. Brightside
mug!
