[1] : The Collaborative International Dictionary of English v.0.48

wellhole \well"hole`\, n.
   1913 webster
   1. arch.
      a the open space in a floor, to accommodate a staircase.
      b the open space left beyond the ends of the steps of a
          staircase.
          1913 webster

   2. a cavity which receives a counterbalancing weight in
      certain mechanical contrivances, and is adapted also for
      other purposes. --w. m. buchanan.
      1913 webster

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Wellhole, definition of term: Wellhole
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