When 2 or more people share the same person sexually often in the same night this action is referred to as a train, a train can be as many as 7 people sharing one girl or boy
When a group of young, rich, up and coming republicans has sex with the same woman, one after the other.
My name's Bart. I will be on the Supreme Court. Pleased to meet you, my name is Jeff, I'll be the CEO of my dad's International Arms manufacturer; and this is John, he will be a five star General like his dad. After you've thrown the dog a bone, I'll introduce you to the rest of the guys in the train.
Basically 3somes, 4somes, etc. A group of peoplefuckingone person which means that ONE person got a TRAIN ran on them.
"Ayee you remember Bailey? Me and my homeboys ran a train on her ass" "Well shit ain't no telling who the daddy is now" "I know it ain't me, I nutted on her face" *both laughs hysterically*