Definition of "wellhole" []

• The open space in a floor, to accommodate a staircase. (noun)
• The open space left beyond the ends of the steps of a staircase. (noun)
• A cavity which receives a counterbalancing weight in certain mechanical contrivances, and is adapted also for other purposes. (noun)

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• "In such a chamber they made a little fireplace, its chimney running up on one side of the wellhole by which the chamber was entered."