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