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.