shit stained thumb knuckle
Its when you wipe your ass after a particularly filthy dump and you get a shit stain your thumb knuckle.
Example:
I was pleased to finally get the key to the executive wash room, however Stan Phillips was not pleases to see that I had a shit stained thumb knuckle when I shook his hand at the share holder meeting.
I was pleased to finally get the key to the executive wash room, however Stan Phillips was not pleases to see that I had a shit stained thumb knuckle when I shook his hand at the share holder meeting.