Towerbridging 

When one girl is being taken from behind by one dude and at the same time his buddy fucks here in the mouth and they highfive at the same time. This all results in an extraodinary resemblance of the London tower bridge. Therefore this girl is being towerbridged.

Wow dude thats a hot chick man
for real we got to towerbridge that ass man.
Yeah we gonna be towerbridging tonight!

Towerbridging by Lemmen September 29, 2010

Tower Bridging 

A rare but enjoyable activity that requires three; normally one female and two males. The lady enjoys the company of the men sexually, by fellating one whilst fornicating with the other; the familiar twos-up porno film routine. At the point of climax for the gentlemen, they give each other a double high five over the unaware lady's back, like Tower Bridge when a masted ship enters port - the seamen are reaching the dock. Mutual climaxing and a foghorn sound is optional.

Jacques and Bob had met her in the club, and had gone back to the Travelodge together. With only one Durex, Jordan suggested a threesome - one in the south, one in the mouth. The boys enthusiastically agreed and pumped away until, paaaaaaaaarrrpp, they found themselves Tower Bridging. Only the sound of hands clapping and skin slapping filled the slightly shabby room and they both felt a little bit emptier. Apart from Jordan who was a little bit fuller.

Tower Bridging by The Brown Piper May 1, 2007