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horsepower

UK/ˈhɔːsˌpaʊə/US/ˈhɔɹsˌpaʊɚ/
nounB2Common in everyday speech and writing · #7,605 of 15,258neutral

Horsepower is a unit for measuring the power of an engine. Two hundred horsepower, brake horsepower, more horsepower.

James Watt defined it to sell steam engines, by working out what a mill horse could actually do, and he set it generously so no customer would feel cheated. There are two versions, mechanical and metric, and they differ by about one and a half per cent.

Definitions of horsepower

  1. 1nounhorsepowerA unit for measuring the power of an engine.B2

    “The new sports car has a powerful engine with plenty of horsepower.”

horsepower is a unit.

Where it comes from

Horse plus power. James Watt defined the unit in the 1780s from the work a horse could do.

From horse + power: the unit was originally defined as the amount of power that a horse could provide. Both non-metric and metric units of power were derived from effectively identical measurements of the power a draught horse could sustain over several hours, with the difference in watts solely due to different rounding errors to express that power in round numbers in the original non-SI units (ft·lbf/min and kgf⋅m/s respectively).

Etymology from Wiktionary, CC BY-SA

Practise this word

horsepower in the wild

  • There are many different standards and types of horsepower.

    Horsepower

  • The electric horsepower, hpE, is exactly 746 watts, while the boiler horsepower is 9809.5 or 9811 watts, depending on the exact year.

    Horsepower

  • The tax horsepower rating was typically computed not from actual engine power but by mathematical formulae based on cylinder dimensions etc, and varying per country.

    Tax horsepower

  • Power was provided by an EMD 567C 8-cylinder engine that generated 900 horsepower.

    EMD SW900

  • The "900" model number reflected EMD's change to a more horsepower-based naming system at the time.

    EMD SW900

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From Wikipedia, CC BY-SA 4.0. These sentences were written by other people about their own subjects; they are here to show the word at work, not as anybody’s opinion.

From Project Gutenberg, public domain. These sentences are from real books, shown to illustrate the word at work.