wellhole

Century Dictionary and Cyclopedia

1. n. A deep, narrow, perpendicular cavity, as the space from top to bottom of a house round which stairs turn; also, an inclosure in which a balancing-weight rises and falls, etc.
2. n. The well-room of a boat.

Wiktionary

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

GNU Webster's 1913

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