An extraordinarily large or voluminousbowel movement. Named in part for the comic-strip Great Dane, known for his extreme size, and in part for duke, a shortening of the fecal synonym dookie.
"Be careful in that stall man, someone took a massive marmaduke in there. It's filling like 75% of the bowl, and they clearly left it there out of pride. Or maybe the toilet just gave up."