Definitions

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. A vertical water space in a firebox or combustion chamber within a steam boiler.
  • n. A support for the centre of a tunnel.

from the GNU version of the Collaborative International Dictionary of English

  • n. A vertical water space in a fire box or combustion chamber.
  • n. A support for the center of a tunnel.

from The Century Dictionary and Cyclopedia

  • n. A hollow horizontal septum in the furnace of a steam-boiler, which, being filled with water, forms a sort of water-bridge, under and over which the flame of the fuel is caused to pass.

Etymologies

mid- +‎ feather (Wiktionary)

Examples

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