plural diameters
1
: a straight line from one side of something (such as a circle) to the other side that passes through the center point
The dotted line indicates the diameter of the circle.
2
: the distance through the center of something from one side to the other
What is the diameter of the tree trunk?
a pipe with a diameter of two inches = a pipe with a two-inch diameter
Dig a hole that's two feet deep and three feet in diameter.
Cite this Entry
“Diameter.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/diameter. Accessed 18 Jun. 2026.
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