From the movie Shawshank Redemption. Tim Robbins' character, Andy Dufresne, secretly digs a tunnel in his prison cell, and hides the dirt and cement from the wall in his pants legs. To get rid of it without anyone knowing, he takes a stroll out in the yard every day, and with every step shakes a little bit out at a time.
When you have to fart, the action of walking around an area and dispersing a little bit at a time so no one notices.
Verb: to lift up your leg or ass cheek and deliver a rousing fart at the exact same time as a loud noise, to avoid being heard, much like the lead character in The Shawshank Redemption hit the pipe with the stone during the storm.