A term used in the online MOBA League of Legends, usually used by a team that's getting their shit kicked in. It stands for "forfeit at 20", 20 min being the earliest your team can surrender in game.
"Man fuck this. You guys suck dick at this game. The other team is too fed. We should just ff at 20. We can't win"
by Loftydrum May 19, 2016