Merriam-Webster Collegiate Dictionary - crystal

 I. noun  Etymology: Middle English cristal, from Anglo-French, from Latin ~lum, from Greek krystallos — more at crust  Date: 13th century  1. quartz that is transparent or nearly so and that is either colorless or only slightly tinged  2. something resembling ~ in transparency and colorlessness  3. a body that is formed by the solidification of a chemical element, a compound, or a mixture and has a regularly repeating internal arrangement of its atoms and often external plane faces  4. a clear colorless glass of superior quality; also objects or ware of such glass  5. the glass or transparent plastic cover over a watch or clock dial  6. a ~line material used in electronics as a frequency-determining element or for rectification  7. ice 7; broadly methamphetamine in any form when used illicitly  II. adjective  Date: 14th century  1. consisting of or resembling ~ ; clear, lucid  2. relating to or using a ~ a ~ radio receiver CRYSTAL  geographical name city SE Minnesota N of Minneapolis population 22,698