from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A small space, distance, or margin: won by a hairsbreadth.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. a very short distance or a very small amount (as is the width of a hair)
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a very small distance or space
hair's + breadth (Wiktionary)