shartbiscuit

(1) A tiny turd you find in your underwear or lodged in the crack of your bum after a shart, or dodgy fart.

(2) Someone who acts like a bit of a turd.

"Damn! That's the third pair of undies I've lost to shartbiscuits since I became a vegetarian!"

"That shartbiscuit Tony always uses all of the milk but never goes to buy it."