The Collaborative International Dictionary
crystal glass
Flint glass \Flint" glass`\ (Chem.) A soft, heavy, brilliant glass, consisting essentially of a silicate of lead and potassium. It is used for tableware, and for optical instruments, as prisms, its density giving a high degree of dispersive power; -- so called, because formerly the silica was obtained from pulverized flints. Called also crystal glass. Cf. Glass.
Note: The concave or diverging half on an achromatic lens is usually made of flint glass.
Usage examples of "crystal glass".
Before allowing the waiter to pour his wine, he held up the Waterford crystal glass and carefully inspected it for water stains.