/ Dictionary / Index R refractometer: Meaning and Definition of Find definitions for: re•frac•tom•e•ter Pronunciation: (rē"frak-tom'i-tur), [key] — n. Optics. an instrument for determining the refractive index of a substance. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: refractometer (Thesaurus) refractivity refractor Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language