Nappy Tail

When one is tired, their butt muscles are not fully in tune with the rest of the body, and, therefore, tend to sag or droop from their usual, flexed position; the "nappy" referring to the tired state of said person, and the "tail" referring to said person's rear end.

"Boo, get your nappy tail back to bed!"
"Dang, you're droopy! That's one nappy tail you've got there!"

Nappy Tail by @Mr.Toashty March 1, 2017

nappatail 

a nappy a** ponytail

Person 1: oh that girl hair look like crap
Person 2: Crap? no..thats what you call a NAPPATAIL.
Both: DAMMMMMMMn...she need a perm.

nappatail by niquie June 20, 2007