Source : Webster's Revised Unabridged Dictionary (1913)

Spiegeleisen \Spie"gel*ei`sen\, n. [G. spiegel mirror + eisen
   iron.]
   See {Spiegel iron}.

Source : WordNet®

spiegeleisen
     n : pig iron containing manganese; used as a deoxidizing agent
         and to raise the manganese content in making steel [syn:
         {spiegel}, {spiegel iron}]