Definify.com
Webster 1913 Edition
Flint glass
Flint′ glassˊ
.(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
. ☞ The concave or diverging half on an achromatic lens is usually made of flint glass.