/ Dictionary / Index R ratiometer: Meaning and Definition of Find definitions for: ra•ti•om•e•ter Pronunciation: (rā"shē-om'i-tur), [key] — n. (in three-color photography) a device for determining the exposure factors of the filters to be used. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ratiocination ration Related Content Daily Word Quiz: censure Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language