Please Define "Overclocking"

Will someone please define "overclocking"?

 

[size=-1]Running your processor at a speed faster than it's rated. Most processors can run faster than their rated speed with some sacrifice of reliability.

Or:
[/size] Any adjustments made to computer hardware (or software) to make its CPU run at a higher clock frequency than intended by the original manufacturers. Typically this involves replacing the crystal in the clock generation circuitry with a higher frequency one or changing jumper settings or software configuration.

If the clock frequency is increased too far, eventually some component in the system will not be able to cope and the system will stop working. This failure may be continuous (the system never works at the higher frequency) or intermittant (it fails more often but works some of the time) or, in the worst case, irreversible (a component is damaged by overheating). Overclocking may necessitate improved cooling to maintain the same level of reliability.