ˈ ̷ ̷ˌ ̷ ̷ noun
1. : the hole, pit, or shaft of a well
2.
a. : the open space in a floor or through a series of floors for the accommodation of a staircase
b. : the open space about which the stairs of a winding or circular staircase turn
3. : a cavity for movement of a counterbalance or similar mechanical device