MSTU Posted in M Best definition MSTUinternet Acronym: My Shit’s Totally Uber. An acronym used by people online to describe their position or relevance in a video game. Player A: Dude, MSTU! Player B: Shutup, you suck! How satisfied are you with the definition? Looking for MSTU meaning? Delighted that you discovered the greatest determine on our web site! Recently this definition was actually observed 2 times.