Woosher Share definition Flag A Woosher is a sub-machine gun and most of the times it would be a Mac 10 or Mac 11. Commonly used as slang in urban London environments. Roadman 1: "That youte's getting bare rude ya know" Roadman 2: "Yeah lemme back out the woosher on him" Woosher by mandxwn March 1, 2019 Get the Woosher mug.