/ Dictionary / Index R radiant flux: Meaning and Definition of Find definitions for: ra'diant flux' Pronunciation: [key] — Physics. Physics. the time rate of flow of radiant energy. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiant energy radiant heat Related Content Daily Word Quiz: portent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language