1. Ironic, or amusingly hypocritical
accusation.
An accusation that just does not work, but applies to the one accusing.
Or
2. Something
false that is so outrageously
off the mark, it's ridiculous or preposterous.
Just so wrong, that it's funny.
Example:
K-Fed: That's
the last straw, Britney! Dammit, I made you. Remember that bitch.
You're nothing without ME! If you pull this shit with me again, I'll leave you in a
new york minute.
Britney: That's rich, Kevin. And new york minute was a terrible movie.
K-Fed: That's it! I'm sick of you not knowing basic English Idioms. I don't know what I ever saw in you. It's over!
OR
Eric: Yo, guys, these Mexicans in my class keep saying the dumbest shit in Spanish.
Tyler: What are they from Spain or something?
Eric: No... They're Mexicans, - they're from Mexico!
Tyler: Wait but.. they speak.. shit.
Joseph: Oh that's rich! FAIL!