The inability of a computer system or related device to operate reliably or to operate at all. A common cause of system failure is loss of power, which can be minimized with a battery-powered backup source until all devices can be shut down. Within a system, electronic failures generally occur early in the life of a system or component and can often be produced by burning in the equipment (leaving it turned on constantly) for a few hours or days. Mechanical failures are difficult to predict but are most likely to affect devices, such as disk drives, that have moving parts.

ETYM From Fail.
1. An act that fails.
2. An event that does not accomplish its intended purpose.
3. An unexpected omission.
4. Lack of success.