Literally, "best friends just friends". Used to describe a guy and a girl who attend events, like a party, together but as strictly friends. Similar to a mutually consensual friend zone.

Origin: Tessa's apartment in Phoenix, 2012. From the Latin, "Justus Friendsus".
Jack and Jill roll up to a party. Megan, who likes jack, says "Hey Jack, who's the girl?"
Jack says, "Don't worry, we're just BFJF."
by Twig's BFGF August 18, 2012
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