timer

noun

1. a person or thing that times.
2. a person who measures or records time.
3. a device for indicating or measuring elapsed time, as a stopwatch.
4. a device for controlling machinery, appliances, or the like, in a specified way at a predetermined time: Please put the roast in the oven and set the timer to cook it for two hours.
5. (in an internal-combustion engine) a set of points actuated by a cam, which causes the spark for igniting the charge at the instant required.

noun

1. a device for measuring, recording, or indicating time
2. a switch or regulator that causes a mechanism to operate at a specific time or at predetermined intervals
3. a person or thing that times