Popped Mattress 

When two men share the same room and sleep on different beds, they eventually get to know each other and discover their homosexuality. After having gay sex, the taker is considered to have had his "Mattress Popped", and therefore sleep on the same bed afterwards.

Makes more since if one slept on an airbed beforehand, where the definition comes from.

Brent: Hey, do Matt and Shane still live together in two different beds?

Shawn: Nah, Matt gave Shane a Popped Mattress and now they share a bed.

Popped Mattress by thetwixter June 11, 2010