Webster's Revised Unabridged Dictionary · 1913

Crystal

Crystal (kris"tal) , noun

[Old English cristal, French cristal, Latin crystallum crystal, ice, from Greek kry`stallos, from kry`os icy cold, frost; compare Anglo-Saxon crystalla, from Latin crystallum; prob. akin to English crust. See Crust, Raw.]

1.
(Chemistry & Mineralogy) The regular form which a substance tends to assume in solidifying, through the inherent power of cohesive attraction. It is bounded by plane surfaces, symmetrically arranged, and each species of crystal has fixed axial ratios. See Crystallization.
2.
The material of quartz, in crystallization transparent or nearly so, and either colorless or slightly tinged with gray, or the like; -- called also rock crystal. Ornamental vessels are made of it. Compare Smoky quartz, Pebble; also Brazilian pebble, under Brazilian.
3.
A species of glass, more perfect in its composition and manufacture than common glass, and often cut into ornamental forms. See Flint glass.
4.
The glass over the dial of a watch case.
5.
Anything resembling crystal, as clear water, etc.
The blue crystal of the seas. — Byron
Collocations (4)
Blood crystal , See under Blood.
Compound crystal , See under Compound.
Iceland crystal , a transparent variety of calcite, or crystallized calcium carbonate, brought from Iceland, and used in certain optical instruments, as the polariscope.
Rock crystal or Mountain crystal , any transparent crystal of quartz, particularly of limpid or colorless quartz.

Crystal , adjective

Consisting of, or like, crystal; clear; transparent; lucid; pellucid; crystalline.
Through crystal walls each little mote will peep. — Shakespeare
By crystal streams that murmur through the meads. — Dryden
The crystal pellets at the touch congeal, And from the ground rebounds the ratting hail. — H. Brooks