A shit, having the consistency of toothpaste, that contains enough mass so as it stacks upon itself it will create a pile of shit in the toilet bowl that breaches the water level in the bowl. The pile of crap in the toilet will resemble a volcano. (Vesuvius is a famous volcano in Italy.)
An adjective describing a person or thing that is explosive or has explosive tendencies. Useful in, but not limited to, describing sports stars, their skills, and their tempers.
When Reggie Bush gets the ball in his hands, he becomes absolutely vesuvius!
Oh my God! Marcus Thames hits another vesuvius home run!