The act of strolling into your local supermarket and heading toward the fruit and veg section. Where you start to masturbate yourself as vigorous as possible, ending with a creamy substance left all over the potatoes, much like Planking
became an internet sensation many have taken to Mashing in much the same way.
Andrew: "Look at that girl over there by the tomatoes, she's got her hands right down her knickers."
Richard: "Who? Catherine? Squatting over the Potatoes? She must have her whole fist up there man."
Andrew: "Yeah, she's Mashing hard dude."