The Collaborative International Dictionary of English v.0.48:

Steelhead \Steel"head`\ (-h[e^]d`), n.
   1. (Zool.) A North Pacific salmon (Salmo Gairdneri) found
      from Northern California to Siberia; -- called also
      hardhead, and preestl.
      [1913 Webster]

   2. (Zool.) The ruddy duck.
      [1913 Webster]