Duck Ass is that obnoxious Meg Ryan-esque hair-do that middle aged a kick in the ass. derived from the way ducks hold their tail feathers up in the air.
Instead of combing your hair straight down in the back, you would comb both sides in towards The Fonz always wore his hair in a Duck's Ass on Happy Days .
The term is made funnier if the fart sounds like quacking duck when expelled from the rectum. when there's a very large crack head duck stuck up your ass.