The act of defecating onto one's chest, then dipping one's ballsack into the feces, leaving a crater. Then peeing into said crater. Creating a mashed potatoes-with-some-gravy inspired look.
My girlfriend is so weird, she let me do Mashed Potatoes to her.

My girl was pissing me off so I gave her some Mashed Potatoes to wake up to.
by Lienad15 March 12, 2014
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an exceptionally heavy ejaculate, generally after prolonged abstinence from sexual activities
The next girl I fuck is gonna get a face full of mashed potatoes
by Shiesty McNasty December 24, 2009
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Said in reference to sneaking up behind someone and humping them in the butt. Giving them ur mashed potatoes means to ejaculate in said person's anus. This is enjoyed by gay men and extremely slutty/kinky girls.
"Come here boy u gonna get sum a deeze mashed potatoes"
by dont worry about it February 12, 2005
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n. A starchy fictional food, looks like glue, or diarrhea. In fiction, it is manifestly made from mashing potatoes (peeled or unpeeled), or sometimes baked, potatoes with a ricer, fork or potato masher.

In real life, it is not possible to mash a potato.

See also Wonka Bar.
"I'm going to make some mashed potatoes."
"That's ridiculous, they don't exist!"
by Some wise guy aha! August 16, 2009
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A pimple on your face that has popped without your knowledgs.
"Damn, Terri had a nasty mashed potato on her cheek this morning..."
by Russell H May 9, 2007
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Meaning a man and a woman that are white and are exchanging their liquids until it looks like mashed potatoes.
Sally made mash potatoes last night with Jim.
by sillywilly1313 June 19, 2014
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