plural milestones
1
: a stone by the side of a road that shows the distance in miles to a specified place
2
: an important point in the progress or development of something : a very important event or advance
—usually + in
The birth of their first child was a (major) milestone in their marriage.
The study marks an important milestone in our understanding of the disease.
Cite this Entry
“Milestone.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/milestone. Accessed 19 Jun. 2026.
Copy Citation
