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A person who comments on someones Facebook wall when its their birthday, and he/she have no idea who it is.
Kayla: Do you know this "Cody" kid?
Giovanna: No why?
Kayla: He posted "happy birthday" on my wall!
Giovanna: What a B-Day Crasher.
Ian: I'm bored.
Austin: Lets go B-Day Crashing later.
Ian: Sure.
by Right guard Power Strip February 14, 2011
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