/ Dictionary / Index P pentosan: Meaning and Definition of Find definitions for: pen•to•san Pronunciation: (pen'tu-san"), [key] — n. Biochem. any of a class of polysaccharides that occur in plants, humus, etc., and form pentoses upon hydrolysis. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pentomic pentose Related Content Daily Word Quiz: feline Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language