timer

Short definition from Wiktionary

Noun

1. 1
   Agent noun of time: someone or something that times: A device used to measure amounts of time.
2. 2
   Agent noun of time: someone or something that times: Any electronic function that causes a device to be able to do something automatically after a preset amount of time.
3. 3
   Agent noun of time: someone or something that times: A person who records the time elapsed in a sporting event.
4. 4
   One who has done something a certain number of times.
5. 5
   One characterized by a certain time or time frame, such as their work hours.