nelson

Noun. Describes a piece of feces partially protruding out of a dog's anus but not fully ejected; caused by the involuntary sphincter contraction during sudden fear, surprise, or sheer terror; the noun can be modified to describe how far out the feces made it, i.e.: quarter nelson, half nelson, full nelson.

Wow, did you see the green half nelson on that poor doggie when that bear jumped out of the bushes?