Johning is the act of making excuses for your loss upon losing a game, the most popular explanation being a "faulty" controller. It's most commonly seen among Smash Brothers and FPS (CoD, Valorant, OW, etc) gamers. Someone who frequently johns after a game is called a john, Mr. John or simply John. See also "Salty".
An example of johning:
(Player 1 attempts to perform a recovery but fails miserably, ending the match)
Player 2: Ha! I won fair and square!
Player 1: Dude, my controller was definitely faulty. Those buttons were sticky, thats why I didn't get my up special.
Player 2: You're blatantly johning, were you even *trying* to recover?