When a skier is mimicking a style of skiing made popular in the 1980's. This particular style is very similar to what was known as parallel skiing, which has now been deemed out of date and very uncool with the advent of shaped skis. One can identify this style if a skier has a their skis together, is putting pressure on the back of the skis, has a ridiculous amount of body rotation, flails their poles about in a wide radius, and is wearing brightly colored one-piece ski suits also from the 1980's.
This term originated from alpine ski racers in the Allegheny Ski Conference in reference to people they would see skiing in resorts located in the Pocono Mountains in Pennsylvania.
Look at that yeti doing the Pocono Shuffle in jeans! (laughter typically ensues)