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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.

Mercedes' rivals were pushing for the compression ratio to be measured at operating temperature.

From BBC • Feb. 28, 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

The compression ratio is a measurement of the cylinder displacement between the two extremes of the piston stroke.

From BBC • Feb. 18, 2026

Mercedes' rivals have complained to governing body the FIA that the former champions have found a way to circumvent the rules regarding compression ratio.

From BBC • Feb. 9, 2026

The original flight engine had a compression ratio of 4.4:1.

From The Wright Brothers' Engines and Their Design by Hobbs, Leonard S.

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