Surge
An unexpected increase in voltage in an electrical current that causes damage to electrical equipment. For example, the standard United States voltage is 120V, if an electrical current above this rating was to come through a power outlet for more than three nanoseconds this would be considered a surge, anything less is considered a spike.
Hardware devices such as surge protectors are designed help prevent any surges and spikes from damaging any electrical equipment by. All electrical devices including your computer should have a surge protector to help prevent them from becoming damaged when an electrical surge occurs.
Also see: Power definitions, Spike