1.One who's level of intelligence is comparable to that of their own
ass.
2.One who's actions suggest that they might be thinking with their own
ass, though it, like their brain, lacks the ability to make intelligent decisions.
See also dumnass
dum ass
dumn ass
(Don't spend too much time on these alternatives, sperm-for-brains. They all mean the same thing.
Jesus. Dumass.