Definition of "timer"

Agent noun of time: someone or something that times.

1. A device used to measure amounts of time.  examples

2. Any electronic function that causes a device to be able to do something automatically after a preset amount of time.  examples

3. A person who records the time elapsed in a sporting event.  examples

One who has done something a certain number of times.  examples

One characterized by a certain time or time frame, such as their work hours.  examples