The Collaborative International Dictionary of English v.0.48:

Bosh \Bosh\, n.; pl. Boshes. [Cf. G. b["o]schung a slope.]
   [1913 Webster]
   1. One of the sloping sides of the lower part of a blast
      furnace; also, one of the hollow iron or brick sides of
      the bed of a puddling or boiling furnace.
      [1913 Webster]

   2. pl. The lower part of a blast furnace, which slopes
      inward, or the widest space at the top of this part.
      [1913 Webster]

   3. In forging and smelting, a trough in which tools and
      ingots are cooled.
      [1913 Webster]