When someone gets drunk and throws up on a bar/restaurant table. In order to have successfully pulled off a four-sided waterfall, the person must have consumed such a large volume of alcohol that the liquid pours down all four sides of the table uninterrupted as if cascading from their mouth to the table, and finally down to the floor.
Friend 1: Hey guys! Check it out! Jon is throwing up on the table!
Friend 2: Dude, how much did he drink? It's totally spilling off the sides.
Friend 1: Looks like he made the Ole' Four-Sided Waterfall....