See snowballing (after ejaculation in someone's mouth, they pass it to another person, or the person who came in the first place). Avalanching is passing said 'snowball' down a line of people...thus, an avalanche.
Gamma Alpha Phi were busy avalanching at their toga party, and didn't notice the cops at the door.
An act of Corprophelia in which one deficates at the highest point of a partner's body, that being the top of the head or shoulders, the goal being to create an avalanche of piping hot fecal matter down said partner's body.
George Bush is totally "avalanching" the American people.