crystal

crys·tal

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

Origin: Middle English cristal, from Old French, from Latin crystallum, from Greek krustallos, ice, crystal; see kreus- in Indo-European roots.