A term created by Gary (lastname classified); originally meant to be used when someone says or does something gay, but later turned out to also be a term used when something or someone did something stupid.
Boy 1:Dude, that guy looks so hot.
Boy 2:You bein gay Tom.
Boy 1: All we gotta do is smack him and he will give us the money.
Boy 2: Bein gay Tom, that's a stupid idea.