If you fail, you sucked so badly at something that your incredibly suckiness broke the Universe, made angels cry, and made God piss blood. To fail is to not succeed ... in an embarrassing, tardish manner. Fail can be used either as one word, in a sentence, or as part of a complicated rant. Words such as 'uber' or 'mega' can also be added. Fail can also be used as a prefix for another word, such as 'boat'. Do not overuse it, or you will fail.
What the hell? You fail.
You are made of fail.
Get back on the failboat, Morgan.