KSI stands for one thousand pounds per square inch. Or a fat Neek who cannot box at all. And has a dead trim as well as a shite beard.
Girl 1: EWWW! You know KSI that fat Neek?.
Girl 2 : Yeah he's so fat and ugly and bad at boxing. And don't get me started on his dead trim LMAO.
Girl 1: Also his beard is shit.