A female (or male) performs fellatio on a group of men consecutively, then immediately repeats the process in reverse order. Whomever goes last in the first round goes first in the second round, and so on. The name is derived from fantasy sports, where a 'snake-style draft' is conducted in the same fashion.
Person One: She gonna snake?
Person Two: Yeah let's put Mike last because he's a rapid reloader
Person Three: Snaking is when...