Hy"drate (?), n. [Gr. "y`dwr water: cf. F. hydrate.] (Chem.) (a) A compound formed by the union of water with some other substance, generally forming a neutral body, as certain crystallized salts. (b) A substance which does not contain water as such, but has its constituents (hydrogen, oxygen, hydroxyl) so arranged that water may be eliminated; hence, a derivative of, or compound with, hydroxyl; hydroxide; as, ethyl hydrate, or common alcohol; calcium hydrate, or slaked lime.

Hy"drate (?), v. t. [imp. & p. p. Hydrated (?); p. pr. & vb. n. Hydrating (?).] To form into a hydrate; to combine with water.

• (chemistry) a solid compound containing or linked to water molecules
  
• to take up, consume or become linked to water
       A lotion can hydrate the skin.