Meaning of heptahydrate

hep•ta•hy•drate

Pronunciation: (hep"tu-hī'drāt), [key]
— n.
  1. 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.