A new-ish insult formed from the 2 words poop and ass. I first heard my three year old cousin say it to his mom. People who eat the poopass are certified Shit-Eaters, they guzzle it like they get paid to. A synonym for poopass is Shitassington, meaning you have a butt that no matter how many time you wipe people can still smell it on you. Sometimes it is also used to describe a poopass trait.
1st example
Little cousin: Mommy, mommy.
Auntie: what honey
Little cousin: you eat the poopass
Auntie: Watch your mouth!
Second Example
Me: I think Kim Kardashian has no skill in anything, she can't sing, dance and she's not funny.
Therapist:Would you say she has no skills then?
Me: No she is very skilled in being a poopass, since she's a certified Shitassington.
Therapist: She does eat the poopass.