The act of vaping then giving your significant other a blowjob, blowing the smoker into the urethra and letting the smoke come out making it look like a steam pipe on a train.
When a couple is having sex in a sauna, both dressed in railroad conductor outfits, the woman doggy-style position, and the man doing her from behind. Then, right when the male partner is about to explode with jizz, he takes it out of the ass or vagina and points his penis up in the air and says "All Aboard!!" This is supposed torepresent a steampipe from a train.