Usually consists of 2 girls and three guys; one gay, one bi, and one straight. The gay guy is the conducter while the first girl is wearing a strap-on doing him. Then the second guy is giving it to the first girl while the second girl is wearing a strap-on doing him. Finally the straight guy is railing the Second chick to complete the train. ALL ANAL!
Dude last night we found two girls on craigslist who would wang train for $450.