/ Dictionary / Index H heptahydrate: Meaning and Definition of Find definitions for: hep•ta•hy•drate Pronunciation: (hep"tu-hī'drāt), [key] — n. a hydrate that contains seven molecules of water, as magnesium sulfate, MgSO&multiplydot;7HO. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. heptahedron heptamerous Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language