A term used by most to describe anything unfortunate, undesirable, foolish, or non-stimulating.
Guy 1 - "Hey, did you see the race on sunday?"
Guy 2 - "Yeah, nobody crashed the entire time. Pretty gay."
Girl 1 - "How was your date with Joshua on Saturday?"
Girl 2 - "It was pretty gay. He didn't make a move on me the whole night."