crystal

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts.
2. n. The unit cell of such a pattern.
3. n. A mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces.
4. n. A natural or synthetic crystalline material having piezoelectric or semiconducting properties.
5. n. An electronic device, such as an oscillator or detector, using such a material.
6. n. A high-quality, clear, colorless glass.
7. n. An object, especially a vessel or ornament, made of such glass.
8. n. Such objects considered as a group.
9. n. A clear glass or plastic protective cover for the face of a watch or clock.
10. n. Slang A stimulant drug, usually methamphetamine, in its powdered form.
11. adj. Clear or transparent: a crystal lake; the crystal clarity of their reasoning.

Century Dictionary and Cyclopedia

1. n. In chem. and mineralogy, a body which, by the operation of molecular attraction, has assumed a definite internal structure with the form of regular solid inclosed by a certain number of plane surfaces arranged according to the laws of symmetry. The internal structure is exhibited in the cleavage, in the behavior of sections in polarized light, etc. The external form is discussed under crystallography (which see). Crystals are obtained in the laboratory either by fusing substances by heat and allowing them gradually to cool, or by dissolving them in a fluid and then abstracting the latter by slow evaporation; also by the direct condensation of a vapor produced by sublimation, as in the case of arsenious oxid, in the same way that snow-crystals are formed directly from water-vapor in the upper atmosphere. The name was first applied to the transparent varieties of quartz, specifically called rock-crystal.
2. n. Glass. Glass of a high degree of transparency and freedom from color. It is heavier than ordinary glass, because containing much oxid of lead.
3. n. Fine glass used for table-vessels or other table-service, or for ornamental pieces. The term is sometimes used as synonymous with cut glass.
4. n. The glass cover of a watch-case.
5. n. A substance resembling rock-crystal or glass in its properties, especially in transparency and clearness.
6. n. In heraldry, the color white: said of that color when described in blazoning a nobleman's escutcheon, according to the system of blazoning by precious stones; pearl, however, is more commonly used.
7. n. A very fine wide white durant, once used for making nuns' veils.
8. n. In optics. See refraction.
9. Consisting of crystal, or like crystal; clear; transparent; pellucid.
10. n. An English trade-name for a fine quality of white sugar.

Wiktionary

1. n. 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.
2. n. countable A piece of glimmering, shining mineral resembling ice or glass.
3. n. uncountable A fine type of glassware, or the material used to make it.
4. n. uncountable, slang crystal meth: methamphetamine hydrochloride.

GNU Webster's 1913

1. n. (Chem. & Min.) 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. n. 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. Cf. Smoky quartz, Pebble; also Brazilian pebble, under Brazilian.
3. n. A species of glass, more perfect in its composition and manufacture than common glass, and often cut into ornamental forms. See Flint glass.
4. n. The glass over the dial of a watch case.
5. n. Anything resembling crystal, as clear water, etc.
6. adj. Consisting of, or like, crystal; clear; transparent; lucid; pellucid; crystalline.

WordNet 3.0

1. n. a protective cover that protects the face of a watch
2. n. glassware made of quartz
3. n. a rock formed by the solidification of a substance; has regularly repeating internal structure; external plane faces
4. n. colorless glass made of almost pure silica
5. n. a solid formed by the solidification of a chemical and having a highly regular atomic structure
6. n. a crystalline element used as a component in various electronic devices