From WordNet (r) 2.0 (August 2003) [wn]:
hydrate
n : any compound that contains water of crystallization
v 1: supply water or liquid to in order to maintain a healthy
balance; "the bicyclists must be hydrated frequently"
2: become hydrated and combine with water
3: cause to be hydrated; add water or moisture to; "hydrate
your skin" [ant: dehydrate]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Hydrate \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.
[1913 Webster]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
Hydrate \Hy"drate\, v. t. [imp. & p. p. Hydrated; p. pr. & vb.
n. Hydrating.]
To form into a hydrate; to combine with water.
[1913 Webster]