A way of replacing the need to
apologize or to say sorry, often by using this term to ease the tension of the situation. To make one seem not as
responsible of his or her mistakes. my bad can also be an
alternative term of equal meaning.
1: I had sex with your
girlfriend last night.
2:
What the hell?? What kind of friend are you???
1: Aw man, my fault! (or "my bad!")
2: Man
it's cool, since you said my fault.