A measurement of the amount of power a car engine can produce.

In metric units, one horsepower = 746 watts or roughly the power produced by twelve 60-watt light bulbs.

An engine's horsepower measured without the loss in power caused by the gearbox, generator, differential, water pump, and other auxiliaries; determined by a brake attached to the drive shaft and recorded on a dynamometer (device used in testing for efficiency and torque).