The act of butt chugging from another person's rectum.
Person "A" first performs a
classic butt
chug. Next, while maintaining hold of the alcohol of
choice inside their rectum and hose still attached, the other end of the hose is inserted into the rectum of person "B". Then person "A" expels the alcohol through the hose and into the rectum of person "B" thus completing the Devil's Waterslide.