variator
/ˈværiˌeɪtər/Definitions
1. noun
A device that varies the output of a machine, especially an engine or generator, by altering the amount of fuel or air it receives.
“The variator on the motorcycle’s engine allowed it to adjust its speed to match the terrain.”
2. noun
A device that varies the amount of voltage or current supplied to a circuit.
“The variator in the power supply helped to regulate the voltage output.”