Shitfinger

v. - To intentionally collect shit (feces, including dingleberries, butt sweat, etc.) onto one's finger (commonly the middle finger, being the longest) and, upon exiting the bathroom or other relief area, then seek out a particularly intolerant, insufferable, jerky, arrogant, drunk, or otherwise undesirable person (see also: shithead) and proceed to approach them from behind (or sneak up on them), grab them by the face, and stick the shit-greased finger past their lips and into their gums (but not beyond, so as not to get bitten). This act is one of extreme boldness, bravery & conviction, and should be reserved only for the worst offenders and/or situations where one can escape quickly and with ease. "Once you figure out what it is, then you realize someone did it on purpose."