The personality a person adopts for their Facebook profile, which may or may not be how they are in person.
Man that guy is annoying! All he does is bash Obama and talk about politics.

Oh, that's just his Facebook personality. He is totally fun to party with.
by LisaGsuperfly December 2, 2013
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(Abbreviated to FMPD) Someone who portrays themselves on Facebook completely differently to how they actually are/behave in real life.

i.e A quiet introvert in real life, but who frequently comments, makes jokes/banter over Facebook. Polar opposite personalities
"That Tommy has got serious Facebook Multiple Personality Disorder! Quiet as a mouse in real life... yet on FB he's the life and soul of the party..."
by BobajobRob February 7, 2012
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