Double Belgium

A single Belgium occurs when a partner about to receive penetration is expecting a slow, manageable entrance but is instead surprised by a hard and fast penetrative strike. (much like Germanys attack through Belgium in world war 1)

A double Belgium occurs when a third person performs a single Belgium at the same time as the initial partner performs theirs, leaving one person to both give, and receive, a single Belgium simultaneously.

Ted: Bro did you bang Jackie last night?
Jeff: Yeah bro I gave her a Belgium, she's probs still sore. Then Old mate stevo came up behind me and made it a Double Belgium.