Source : Webster's Revised Unabridged Dictionary (1913)

Crucible \Cru"ci*ble\ (kr[udd]"s[i^]*b'l), n. [LL. crucibulum a
   hanging lamp, an earthen pot for melting metals (cf. OF.
   croisel, creuseul, sort of lamp, crucible, F. creuset
   crucible), prob. of German origin; cf. OHG. kr[=u]sul, LG.
   kr["u]sel, hanging lamp, kroos, kruus, mug, jug, jar, D.
   kroes cup, crucible, Dan. kruus, Sw. krus, E. cruse. It was
   confused with derivatives of L. crux cross (cf. {Crosslet}),
   and crucibles were said to have been marked with a cross, to
   prevent the devil from marring the chemical operation. See
   {Cruse}, and cf. {Cresset}.]
   1. A vessel or melting pot, composed of some very refractory
      substance, as clay, graphite, platinum, and used for
      melting and calcining substances which require a strong
      degree of heat, as metals, ores, etc.

   2. A hollow place at the bottom of a furnace, to receive the
      melted metal.

   3. A test of the most decisive kind; a severe trial; as, the
      crucible of affliction.

   {Hessian crucible} (Chem.), a cheap, brittle, and fragile,
      but very refractory crucible, composed of the finest fire
      clay and sand, and commonly used for a single heating; --
      named from the place of manufacture.

Source : WordNet®

crucible
     n : a vessel made of material that does not melt easily; used
         for high temperature chemical reactions [syn: {melting
         pot}]