Chillin. Hangin. Straight kickin it or cold lampin. Laying low and staying cool. Originally a line from Putney Swope, the literal meaning is to be sitting in a Cutlass Supreme.
In the late 80s and early 90s NYC, muggings/ robberies/chain snatching happened all the time. "Layin' in the cut" referred to waiting in a covered location, ie btw 2 buildings or in an alley, for the right opportunity to jump someone or rob.