flint glass

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A soft, fusible, lustrous, brilliant lead-oxide optical glass with high refraction and low dispersion.

from The Century Dictionary.

• noun A variety of glass in which the silica is combined with oxid of lead in greater or less quantity.

from the GNU version of the Collaborative International Dictionary of English.

• (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.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A soft, heavy, brilliant glass, consisting essentially of a silicate of lead and potassium. It is used for tableware and in optical instruments.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun optical glass of high dispersion and high refractive index