"Popping off" is a verb used when you're doing extremely well and or performing like a professional/better than anyone in your game. Can also be used when you're being accused of cheating in a video game because the sheer amount of god like skill you possess.
A term that means to go crazy. When you pop off you do really well in a videogame, rant, argument, or school. Its used all the time during casual talk and can hint that they want you to calm down. Popular people use this term loosly and its hard to precisely define it.