Wiktionary
my ass
interj. (context slang vulgar English) Indicates disapproval, disagreement, or disbelief, often with a tone of disregard, disdain, or disgust. pron. (context slang vulgar English) I, myself; oneself in the third person.
Usage examples of "my ass".
Pinched my ass a couple times when I came here looking to make some deals.
Vampire enclaves from both coasts are after me and now Orson Scott Card is going to sue my ass.
I'm not busting my ass after office hours just so you can beinspired to make wiseass remarks.
Then he laid me on the floor on some soft pillows and had me lie on my stomach while he started to fuck me up my ass.