/ Dictionary / Index C compression ratio: Meaning and Definition of Find definitions for: compres'sion ra"tio Pronunciation: [key] — Auto. Auto. the ratio of the cylinder volume enclosed by the piston at its outermost position to the volume enclosed by it at its innermost position. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. compression molding compression wave Related Content Daily Word Quiz: crutiny Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language