When a bunch of girls bump and grind together in a train. Presumably to attract the attention of male counterparts. Usually resulting in one or more males joining the "slut train" to "GET SOME". In a Slut Train, there is a lot of "droppin it" accompanied by multiple body rolls. Usually to dirty rap music on 148th and stark, or in Antons living room.
Ellen: "YEEEEEAH, lets start a slut train guuuurl"
Morgan: "Hell yeah! BRE, HANNAH, SERENA, YOU IN?!?!"
(slut train ensues)
Todd: "Dude, Anton, we need to get in on that slut train, i want to GET SOME!!!!"