Definition: A unit of measure for quantifying power output. Invented by James Watt, the term was originally used to describe how much effort a horse exerted when lugging coal out of a coal mine. One horsepower was the amount of effort one horse put forth in raising 33,000 lbs. one foot in one minute. Engine horsepower ratings are determined on special equipment (See Dynamometer), and are usually expressed as so much "brake" horsepower (the amount of horsepower the engine actually delivers after internal friction and parasitic loses are taken into account).

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