/ Dictionary / Index C companion cell: Meaning and Definition of Find definitions for: compan'ion cell" Pronunciation: [key] — Bot. Bot. any of a number of specialized parenchymal cells adjacent to a sieve tube in the phloem of flowering plants, believed to regulate the flow of nutrients through the tube. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. companionate marriage companion ladder Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language