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A person so fat, that they are named after half of a McDonald's breakfast sandwich, while also implying they have tons of stretch marks. Even stretch marks on their stretch marks. Often used as an endearing term among fat girls.
Fat girl #1: How's it goin' Fatty McStretchmark?

Fat girl #2: Great. On my way to 7-11 to go get some spicey bites, nachos, and rasberry-filled powdered donuts. You?

Fat girl #1: I'll come with you. I need to get all those things too, and a Diet Pepsi to wash it down.
by Thatgirl235 June 28, 2009
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