Ok, simple enough term. Let us clarify though. When we say someone needs to take a drink we are saying a one Mississippi for someone who really drinks but usually a 2 or 3 second count for most people. Basically at least an ounce of beer.

Whats more social then everyone drinkin together? What thats what a social is. Everyone playing drinks together for a few seconds.

A waterfall is a situation where everyone drinks. Now, when a waterfall is in play there is a starting person and an ending person (who is on either side of the starting person depending on whether your going clockwise or counterclockwise.) This starting person can stop anytime they want. Then the next person, once the person before them stops, can stop when they like. This continues until it gets to the last person. Basically you can torture the hell out of a person/people by continuing to drink until they finish their drink.