Idling refers to running a vehicle's engine and the vehicle is not in motion, or when the vehicle drops to its resting point of RPMs. This commonly occurs when drivers are stopped at a red light, waiting while parked outside a business or residence, or otherwise stationary with the engine running. When idling, the engine runs without any loads except the engine accessories, and without the additional fuel via the gas pedal. If the vehicle moves while in gear and idling, The "idle speed" mechanically should be adjusted.

Revolutions per minute is a unit of rotational speed for rotating machines. One revolution per minute is equivalent to 1/60 hertz.