The act of constantly typing someone's name in a Facebook group so their computers "beep" to get their attention. However, the term "beeping" was eventually phased out, replaced with the now common "beening," meaning people have been beeping someone repeatedly.
It can also be used to describe the past tense, as in "Oh man, I just got beened."
(On a Facebook group chat)
Jake: Hey, where's Nicki?
Dave: I dunno, let's try beening her.
Jake: Make me a sandwich!