noun
(countable) A solid composed of an array of atoms or molecules possessing long-range order and arranged in a pattern which is periodic in three dimensions.
(countable) A piece of glimmering, shining mineral resembling ice or glass.
(uncountable) A fine type of glassware, or the material used to make it.
(uncountable, slang) Crystal meth; methamphetamine hydrochloride.
(obsolete, figuratively, usually in the plural) A person's eye.
The glass over the dial of a watch case.
adjective
(literally) Made of crystal.
(figuratively) Very clear; coherent.