/ Dictionary / Index B beta ray: Meaning and Definition of Find definitions for: be'ta ray" Pronunciation: [key] — Physics. Physics. a stream of beta particles. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. beta particle beta receptor Related Content Daily Word Quiz: effervescent Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language