Means: To do something wrong
Usage: "Did your mum buy you that blazer? Fail"
It is nice, just once, for a word of the Yoof to derive from school terminology. But the academic "to fail" - not attaining the required level of educational excellence - has, of course, become bastardised to incorporate any kind of error, from social to stylistic, without the need of a preposition (although the addition of "epic" is often used to highlight when someone has gone really off the rails: "You got off with Tom in 6B? Epic fail"). And who do we have to thank for its burgeoning popularity? As ever, online allegiance in chat rooms and multiplayer gaming, as we guess "fail" is much quicker and easier to type than, "Sorry, I don't like Glee, I think you should get out more."