when a girl gathers a bunch of guys and has sex with them one after another
oh dayam! bree got on that choo choo train last night? what a slut!
A long line of gay guys having butt sex
Dude yesterday I decided to join a choo-choo train and now my butt hurts
When two homosexuals choose to play the rodent game (sticking a rodent into one's bum) and they put a tube between the two, the partner with the rodent inside him farts in order to try and get the rodent to run into his partner's bum.
Wow! did you see that hamster run from Frank's bum to Steves? that was quite a choo choo train