According to thefreedictionary.com it is:
The condition or fact of not achieving the desired end or ends: the failure of an experiment.
One that fails: a failure at one's career.
The condition or fact of being insufficient or falling short: a crop failure.
A cessation of proper functioning or performance: a power failure.
Nonperformance of what is requested or expected; omission: failure to report a change of address.
The act or fact of failing to pass a course, test, or assignment.
A decline in strength or effectiveness.
The act or fact of becoming bankrupt or insolvent.
But with all respect to thefreedictionary.com,
I have much better definition for it:
LOOOOOOOOOOOOOOOOOOOOOL