a homosexual orgy of strategically placing men in a straight line and performing anal sex with the man directly in front of you, whilst receiving it from behind. Unless you're the caboose, which just might be one of the only two spots on the train that receive the least please. The other being the front "Engine."
Matthew and his friends decided to go back to the hotel and form a bob train.
by The Dirk Digler March 27, 2010