The Collaborative International Dictionary of English v.0.48:

Shadrach \Sha"drach\, n. (Metal.)
   A mass of iron on which the operation of smelting has failed
   of its intended effect; -- so called from Shadrach, one of
   the three Hebrews who came forth unharmed from the fiery
   furnace of Nebuchadnezzar. (See --Dan. iii. 26, 27.)
   [1913 Webster]