Said on RPG games, meaning Duel of Fate. You roleplay intense fighting and whoever loses must leave the server / RPG.
The loser usually doesn't leave because it's cyber-world, and then opponent can't actually physically hurt them.
Guy 1: lol, yh sure cnt. fk off plz kty.
Guy 2: DOF dude. DOF. come on.
Guy 1: lolsure. sure dude.