A very difficult Gay sexual act normally consisting of 6 gay men in an orgy. Four of the men are having anal sex , all while underneath them the other two men assume the ball licking position as the other men are fucking doggystyle. In order for the position to work the two men getting it in the ass should need to take a huge shit , or have a bad case of the runs. Immediately after the two men servicing the ass givers cum in the buttholes , the guys who took it in the ass then proceed to shit on the receivers down below .
Hence the phrase Gravy Train because its a bloomin Shitty Gravy like mess afterwards.
We did the Gravy train while my wife was away last week , and my butthole still hurts !!!!!