Usually said by lame high school underclassmen who haven't realized that it's not a cool thing to say, and in turn look like complete idiots to anyone who happened to hear them.
Steve: Oh sure. *attempts to hand Bill his calculator, but accidentally drops it*
Bill: EPIC FAIL!
Steve: Oh sorry, I thought you were cool. No, you can't borrow my calculator.
Jim: And I don't want to be friends with you anymore.
Definition as it pertains to Relativity - Failure so monumental in scale that it has the possibility to rupture the space-time continuum by fracturing the light-cone at the point between the causal past and causal present boundaries because there is no possible way the cause could precede any effect within the same spatial reference frame of the observer.
Definition you're most likely to understand - The result of the physical union of your parents.
Greg: "Oh yeah? What happened?"
Bob: "Turns out my music makes people's ears fall off"
Greg: "Epic fail, no cookie for you!"
Following this conversation, the universe folds in on itself and is oblitera