Mustard Finger

When a person goes to itch the inside of there ass cheeks not knowing that they previously did not wiped good enough. When they pull there finger back out and look at it, it has a light brownish tint covering it from sweat and feces that resembles mustard.

Dude my asshole was itching bad. I should have done a safety swipe before i scratched it because I ended up with mustard finger.