compression ratio

American

noun

Automotive.

the ratio of the cylinder volume enclosed by the piston at its outermost position to the volume enclosed by it at its innermost position.

compression ratio British

noun

the ratio of the volume enclosed by the cylinder of an internal-combustion engine at the beginning of the compression stroke to the volume enclosed at the end of it

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of compression ratio

First recorded in 1905–10

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

See Examples For:

compression ratio

Off track, one of the main focuses of pre-season has been a row between the engine manufacturers over the rules governing the engines' compression ratio.

From BBC ● Feb. 20, 2026

Because their rivals believe they have found a way of exploiting the rule restricting the compression ratio - a measurement of the cylinder displacement between the two extremes of the piston stroke - to 16:1.

From BBC ● Feb. 20, 2026

Rivals believe Mercedes have found a loophole that allows them to run the engine above the permitted compression ratio.

From BBC ● Feb. 11, 2026

And it's not only on compression ratio, but on other things too.

From BBC ● Feb. 2, 2026

From the above it is evident that in order to bring the final compression pressure up to the efficient figure we have determined, a different compression ratio would have to be used.

From Aviation Engines Design?Construction?Operation and Repair by Victor Wilfred Pag?

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023