Similar to the snowball, an avalanche is a sex act in which multiple men ejaculate into a person's mouth and that person then kisses another, forcing all of the semen into the receiving person's mouth.
That bukkake party was going great last night, until Rachel got up and avalanched Dave. Dave will never be the same again.
A sex act in which someone ejaculates into another person's mouth. That person then holds the ejaculate in their mouth for a period of time for no less than 1 hour. After the period of time has passed and the saliva/semen mixture has stewed in their mouth, this person then kisses another and forces the mixture into another person's mouth.
Dave: I picked Dina up for dinner last night, but she gave me the strangest kiss before we left. I think she was eating soup or something before hand, it was so salty.
Greg: Dina? She blew me yesterday afternoon. You think it was an abominable snowball?
Dave: Well fuck, that's the third time this month.