from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A vertical shaft around which a staircase has been built.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A shaft in a multi-story building enclosing a stairway or staircase.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a vertical well around which there is a stairway
From stair + well (a reference to the shaft's usual shape). (Wiktionary)