/ Dictionary / Index R radiation fog: Meaning and Definition of Find definitions for: radia'tion fog" Pronunciation: [key] fog produced by the nocturnal cooling of the surface boundary layer to a temperature at which its content of water vapor condenses. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. radiation belt radiation potential 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