This is the largest "sigh" a human can produce. Usually associated with disdain or disgust , misery and woe, or a women on her period. It comes from the comparison of the large exhaling released by a hippopotamus during the breathing process.
"Oh man i have that paper to do.....SIGHAPOTAMUS!"
"Yo dude my girl just told me shes on the rag, again! SIGHAPOTAMUS!"
"The police are here....AGAIN! SIGHAPOTAMUS!"
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?"