A bunch of guys,assembled like a train, that are linked by their penises in another guy's butt.
I went to the lavatory and saw a six man gay train.
A minimum of three men lined up, each man has their dong inserted into the man standing in front of hims anus with hands on his hips. The man at the back of the train must be black, and the man at the front must have a totally flaccid dong whilst swirling it in a helicopter type motion.
Eugene: "Holy shit look at those fagot's flying down that really steep hill on roller skates with their dicks in each others asses in a train like motion"
Stavros: "That my friend is a gay train express, a special form of the gay train"
Eugene: "I wish i could be in a gay train express"
Stavros: "Me too"