Definition of milestone
- Graduating from college was an important milestone in her life.
the new drug was regarded as a milestone in the treatment of heart disease
These example sentences are selected automatically from various online news sources to reflect current usage of the word 'milestone.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.
: a stone by the side of a road that shows the distance in miles to a specified place
: an important point in the progress or development of something : a very important event or advance
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