Mystery Unknown One, it's a term used for people disguised as an unknown one, and are a mystery for people. It's also used to tag people who never talk about their selves. It's also a name for a Tf2 Server Community's Admin; The name of the community is AoDRP, he gets bullied by spamming Tatsumaki's Rep commands.
???: *walks through the city*
People: Oh, he is mysterious.....
Dick Skinner: Nah he is just Mystery, an AoDRP Admin. His name is Mystery Unknown One, a good admin tbh.
The name of someone with chronic shanking abilities. The only thing going for them its the great southern bundah.
You don't fuck with the Unknown B, he'll tap your nan.
The game where a pan is the best melee weapon that you can obtain
A:hey dude, did you play PUBG last night? I got 2nd place!
B:i played it but in the first 10 minutes i got sniped from someone 2 miles away, also, its actually called player unknown's battlegrounds