/ Dictionary / Index I ionizing radiation: Meaning and Definition of Find definitions for: i'onizing radia'tion Pronunciation: [key] — Physics. Physics. any radiation, as a stream of alpha particles or x-rays, that produces ionization as it passes through a medium. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ionize iono- Related Content Daily Word Quiz: sequester Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language