Popularized by "The Situation" from Jersey Shore. "The Situation" defines it as a combination of a slop tart and a hippopotamus
The Situation: "Deena turns into the Sloppapotamus of the house. Combination of a slop tart and a hippopotamus put together. Sloppa... sloppa... ssssloppatopudus?"
(noun)-Combination of a "slop-tart" and "hippopotamus" as quoted by Mike the "situation" on Jersey shore. In otherwords, a really drunk, sloppy bitch that has no regard for her appearance. AKA Deena, also on Jersey Shore
Deena was falling all over the place and turned into a complete sloppapotamus.