When you catch your grandma in a gangbang. You call her Gangma to basically shorten the two words: Slutty Grandma.
Bob: I caught my grandma in a gangbang... what should I do?
Me: Call her gangma, and join in on the act. It was used before, why not refresh it!
A Call of Duty clan meaning Old School Beat Warriors. If you see this clan in-game you are going to get shit on by these guys. Not very popular but very skilled.
I got owned on Call of Duty when I ran into an OSBW member