/ Dictionary / Index A air equivalent: Meaning and Definition of Find definitions for: air' equiv"alent Pronunciation: [key] — Physics. Physics. a measure of the effectiveness of a material in absorbing nuclear radiation, expressed as the thickness of an air layer (at 0° C and 1 atmosphere) causing the same absorption. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Airedale air express Related Content Daily Word Quiz: illegible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language