Literally means nothing, but generally used as a greeting or goodbye. The phrase may also be used to describe a moment of guys being dudes.
*Kyle walks down hallway*
*Sees friend walking to his direction*
"Hey dude, Posted Up in York!"
"Haha, Posted Up in York!"
*Kyle and friend continue walking to their destination*
To stand in an outdoor area near a cut through or passage around a fence, building, or other physical barrier for the purpose of selling recreational pharmaceuticals. Standing posted in the cut enables the entrepeneur selling said recreational pharmaceuticals to quickly escape if law enforcement approaches as the law enforcement officers' vehicles will hindered by the barrier
Tyrone: Yo, whassup?
Jamal: Nothin' man. Just posted in the cut trying to make some dollar bills, yo.
Tyrone: You better watch out man, I just saw some undercovers around the way.
Jamal: Thanks, Dawg.