An annoying as all fuck "internet meme" or trend used by people who aren't innovative enough to come up with an appropriate term, expression, watch too much Attack of The Show, or spend over 8 hours behind a computer.
Boy 1: Did you see that airplane take off and crash?! Dude, "EPICFAIL"!
Boy 2: Epic----what?
Boy 1: You don't know what "Epic Fail" means, bro?
Boy 2: Being that the word "fail" isn't an adjective, I do now.