from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A stone marker set up on a roadside to indicate the distance in miles from a given point.
- n. An important event, as in a person's career, the history of a nation, or the advancement of knowledge in a field; a turning point.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A stone milepost (or by extension in other materials), one of a series of numbered markers placed along a road at regular intervals, typically at the side of the road or in a median.
- n. An important event in a person's life or career, in the history of a nation, in the life of some project etc.
from the GNU version of the Collaborative International Dictionary of English
- n. A stone serving the same purpose as a milepost.
- n. An event or accomplishment marking a significant advance in an endeavor; a notable achievment.
from The Century Dictionary and Cyclopedia
- n. A stone or pillar set up along a highway or other line of travel to mark distance in miles.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. stone post at side of a road to show distances
- n. a significant event in your life (or in a project)
mile + stone. (Wiktionary)