Used to describe a foul flavor or smell, though not directly comparing the offending taste/odor to ass itself, thus creating a "catch-all" category of troublesome sensory inputs.
An Agent of Secret Stuff(ASS). The existance of ASSes was unknown until they were revealed in youtube celeberty Nigahiga's short-film - "Agents of Secret Stuff".
Guy 1: Ryan's an ASS.
Guy 2: Dude, that's mean!
Guy 1: No, I meant that he's an ASS for the government!
1. Four legged mammal similar in appearance to a horse, albeit a particularly straggly, smelly horse. The donkey belongs to this particular segment of equestrians.