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1 definition by TheDevil'sAdvocate

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."
by TheDevil'sAdvocate September 15, 2011