An acronym describing finishing a task early and making an exit to pursue more meaningful and satisfying activities. i.e. Finish Early, F**k Off.
(Sam:) Tim, did I see you leaving the office at 3pm?
(Tim:) Yeah, not much going on in the world of light fittings today so I fefo'd that shit, went home and jacked it.
Have you heard about the latest meme on Urban Dictionary? you gotta check out FEFO, it's a thing now, everyone's using it... if you don't you're not cool anymore (assuming you were cool in the first place).