A fork of Rural Dictionary
To stand with one arm straight down, with the hand outwards, and the other turned at your side to put two fingers on the inner elbow of the first arm.
"Mr. O'Brien is posted up with his students for this photo I am going to take."
"Sheeeeesh"
To pose against something in a sexually enticing or slutty way usually showing the back side. Like a comfy lean presenting one's ass.
Damn he's really just posted up with all that cake.