Horsepower (noun)

1. A unit of power, equal to 746 watts, used to express the output power of engines and motors.
2. The rate at which work is done; power.
3. The power that a horse is capable of exerting, especially when used to drive machinery.

Origin:

From horse power, early 18th century. originally referred to the power of a horse to do work. later applied to machinery.

Examples:

1. The car has a horsepower of 200.
2. The generator has a horsepower of 50.
3. The engine produces a maximum horsepower of 500.
4. The machine is rated at 5 horsepower.
5. The tractor has a horsepower of 75.