Definify.com
Webster 1913 Edition
Wellhole
Well′holeˊ
,Noun.
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.
2.
A cavity which receives a counterbalancing weight in certain mechanical contrivances, and is adapted also for other purposes.
W. M. Buchanan.