Ass Shoulder
The portion of the body where the upper buttocks meet the hips.
Dude, Carmen Elektra has bangin' ass shoulders. I'd fuck that shit.
ass on your shoulders
Being overly defensive, obnoxious, confrontational, or just generally annoying.
Man, you've really got your ass on your shoulders.
get your ass off your shoulders
This is usually referred to someone who is stuck up or arrogant.
"I wish Mike would get his ass off his shoulders and admit he was wrong for tea-baggin James while he was sleep!"