When you give a girl laxatives to cause her to have diarrhea, flip her over so her ass fills with shit (root beer), and cum on top of the pool of of shit (vanilla ice cream)
Person 1: How did your date go with Sarah?
Person 2: It went great, we saw a movie then I gave her the Root Beer Float in my car
upon finishing the activity of an "upper decker" (shitting in the upper tank of someones toilet) you then dump an entire bottle of dishwashing soap in the tank and then flush the tiolet so the bowl fills up with bubbling shit water....
Tom pulled an upper decker on Bills shitter, and I finished it off making it a root beerfloat!
Where one splooges into someone's mouth and then proceeds to drop a sloppy deuce into their mouth. If the density of the poop is greater than the splooge, then the sploogewill float to the top creating the illusion of a root beer float.
Person 1: "Man I'm hungry for a Root BeerFloat!"
Person 2: *fap*fap*fap* "Say ahhhh..."