Plain English Meaning
A measurement of how much work an engine can do in a given amount of time. One kilowatt is 1,000 watts, and it's another way of saying horsepower — about 1.34 horsepower for every kilowatt.
Full Definition
A unit of power equal to 1,000 watts. Power is the rate at which work is done or energy is used. In aviation performance discussions, kilowatts are sometimes used alongside or in place of horsepower to express engine output, where 1 horsepower equals approximately 0.746 kilowatts.
Context Anchor
Seen in climb performance discussions when aircraft power is shown in metric units instead of horsepower.
Derivation
From the Greek 'kilo' meaning 'thousand,' and 'watt,' named after James Watt, the Scottish engineer who improved the steam engine. So a kilowatt is literally one thousand of the units named after the man who first made power something engineers could measure.