1. [techspeak] The master oscillator that steps a CPU or other digital circuit through its paces. This has nothing to do with the time of day, although the software counter that keeps track of the latter may be derived from the former.
2. vt. To run a CPU or other digital circuit at a particular rate. “If you clock it at 1000MHz, it gets warm.”. See overclock.
3. vt. To force a digital circuit from one state to the next by applying a single clock pulse. “The data must be stable 10ns before you clock the latch.”