The master of a retard, as commonly seen in public schools since the initial passage of the Individuals with Disabilities Education Act, which mandated the inclusion of retards into standard education settings. These retards need constant individual supervision from tardmasters.
"Dude, did you see that retard flip his shit in gym earlier? His tardmaster had to take him down!"
when you're holding up your phone and making faces at it, as though you are taking a selfie, but you're really taking a picture of the person across from you or the wall or anything else that seems interesting but you don't want to be caught dead taking a picture of.
This action is often made more convincing by wiggling the eyebrows or opening the mouth, to pretend you're trying to get a Snapchat filter to work.
FRIEND A: "Did you just take a stealthie of me?"
FRIEND B (turning phone around): "no I was just using snapchat's new filter, see?"