HY'DRATE, noun [Gr. water.] In chimistry, a compound, indefinite proportions, of a metallic oxyd with water. A hydrate is a substance which has formed so intimate a union with water as to solidify it, and render it a component part. Slaked lime is a hydrate of lime.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI