bum chain 

A bum chain is an intimate form of the conga, it is usually performed in gay clubs where the participants form a chain, the links being where one mans penis is inserted into the arse of the man in front and so on and so forth, until the chain is complete.

Hey bob, look at that great big group of queers over there, they'll probably be be making a bum chain later

bum chain by Codiak July 31, 2003