/ Dictionary / Index A alpha receptor: Meaning and Definition of Find definitions for: al'pha recep"tor Pronunciation: [key] a site on a cell that, upon interaction with epinephrine or norepinephrine, controls vasoconstriction, intestinal relaxation, pupil dilation, and other physiological processes. Also calledCf. beta receptor. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. alpha ray alpha rhythm 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