Top definition
The sudden avalanche of birthday greetings posted on facebook etc when someone notices its your birthday....particularly funny when someone incorrectly posts Happy Birthday and everyone follows suit!
Fran: "Michael, your birthday is definitely tomorrow isnt it?"

Michael: "10 years Fran, its been 10 years. Why?"

Fran: "Your cousin's started a Birthday Avalanche on your Fb profile!"
by Fran P April 17, 2009
Get the mug
Get a Birthday Avalanche mug for your dog Rihanna.