Sometimes shortened as "vish-ass," a bulbous, bangin' ass typically packed tightly into sheer pants having the appearance or giving the impression of being under high load or pressure, as if the pulling of a single thread from said pants might cause a fairly significant, immediate discharge or rearrangement of space and matter, possibly resulting in bodily harm to the casual observer.
I was in Subway today and this smoking-hot chick with a vicious ass nearly gave me a heart attack.
The sphincter muscles controlling closure of the anus, responsible for smooth operation of the final step in the digestive process, defecation. Poosaw is the compound word of poo and saw, literally referring to the cutting operation the poosaw performs on excrement.
I couldn't crap for a week. My doc blamed it on my overactive poosaw.