Someone who works at a direct care facility and helps to take care of people with developmental disabilities--especially ones with genetic cognitive disabilities. Essentially a baby sitter for retarded people.
Friend: Hey, let's go watch the game tonight!
'Tard Sitter: Sorry, bro. I can't go out to the game tonight because I picked up an extra 'tard sitting shift tonight.
The opposite of a half sitter.
In a half-sitter, one poops without having made full contact with the toilet, whereas in a double sitter, one has already wiped and washed, and after concluding the poop must return very soon after.
A: “Damn bro, why did you walk out of the bathroom, stop, and immediately turn around and go back?”
B: “My poop turned into a double sitter”
A poop that is so long that one end sits in the bottom hole of the toilet while the other comes up out of hole and rests on the rim of the toilet hole. Said poop may or may not protrude from the water, which begins to cross over into the rim sitting iceberg territory.