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

1. \Crys"tal\ (kr?s"tal), n. [OE. cristal, F. cristal, L.
   crystallum crystal, ice, fr. Gr. ????, fr. ???? icy cold,
   frost; cf. AS. crystalla, fr. L. crystallum; prob. akin to E.
   crust. See {Crust}, {Raw}.]
   1. (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. 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. 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.
   
   {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.
   
   

2. \Crys"tal\, a.
   Consisting of, or like, crystal; clear; transparent; lucid;
   pellucid; crystalline.
   
         Through crystal walls each little mote will peep.
                                                  --Shak.
   
         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.
   
   

Concurrent Representation of Your Space-Time ALgorithms.

A recursion equation parallel language.

["A Parallel Language and its Compilation to Multiprocessor Machines or VLSI", M.C. Chen, 13th POPL, ACM 1986 pp.131-139].

(Ezek. 1:22, with the epithet "terrible," as dazzling the spectators with its brightness). The word occurs in Rev. 4:6; 21:11; 22:1. It is a stone of the flint order, the most refined kind of quartz. The Greek word here used means also literally "ice." The ancients regarded the crystal as only pure water congealed into extreme hardness by great length of time.