/ Dictionary / Index R RDA: Meaning and Definition of Find definitions for: RDA Pronunciation: [key] (not in technical use) recommended daily allowance. Cf. See Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Rd RdAc Related Content Daily Word Quiz: longevity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language