/ Dictionary / Index M medullary ray: Meaning and Definition of Find definitions for: med'ullary ray' Pronunciation: [key] (in the stems of woody plants) one of the vertical bands or plates of unspecialized tissue that radiate between the pith and the bark. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. medullary medullary sheath 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