/ Dictionary / Index P pentahydrate: Meaning and Definition of Find definitions for: pen•ta•hy•drate Pronunciation: (pen"tu-hī'drāt), [key] — n. Chem. a hydrate that contains five molecules of water, as potassium molybdate, KMoO&multiplydot;5HO. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. pentahedron pentahydric Related Content Daily Word Quiz: ounterfeit Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language