Biffon Bridge 

The bridge of tissue between the anus and vagina, on which a mans hairy bean bag is likely to 'biff' against during enthusiastic coitus.

I could hardly hear the telly for the noise of my nads slapping against her biffon bridge

Biffon Bridge by steviestevoid June 28, 2011

Biffin's Bridge 

The area between the vagina and the anus..cross if you dare!

Well it slipped out of the hole, across Biffin's Bridge and up the ante!

Biffin's Bridge by Tracey August 29, 2003