Flatulence that has passed faeces nearing readiness for excretion in the rectum prior to ventilation. The flatulence therefore takes on some extra characteristics related to the faeces, and can be readily identified as a Poo Fart by those nearby.
I just did a poo fart and now my wife is insisting I go to the toilet. Instead, I will simply do more as I am becoming increasingly dissatisfied in this shambles of a marriage.