What is Seatcheck?
1.
Calling "seatcheck" is alot like calling out "shotgun" in the fact that it is used to claim your: chair, sofa spot, futon, stair, whatever your seat may be, when you want to get up for a moment. It lets everyone around know that that spot, while vacant, is still occupied.
"Man, I'm thirsty. Seatcheck!"
See