- The definition of a milestone is a notable event that causes some change to occur or that marks a specific point in the development of a person or project.
- An example of a milestone is when the court makes a sweeping change in the civil rights law.
- An example of milestone is a person's 16th birthday.
Your twenty-first birthday is a milestone in your life.Licensed from iStockPhoto
- a stone or pillar set up to show the distance in miles to or from a specified place
- a significant or important event in history, in the career of a person, etc.
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- A stone marker set up on a roadside to indicate the distance in miles from a given point.
- 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.