millimeter
noun
mil·li·me·ter
ˈmi-lə-ˌmē-tər 
variants
US millimeter
or British millimetre
: a unit of length equal to 1/1000 meter see Metric System Table
Examples of millimeter in a Sentence
Recent Examples on the Web
The entire photonic lantern measures less than half a millimeter in length.
—
Aamir Khollam, Interesting Engineering, 11 Mar. 2026
Over millions of years, metals in the surrounding seawater form coatings of iron and manganese oxides, with thicknesses ranging from a few millimeters to a few decimeters, depending on the age of the seamounts.
—Leonardo MacElloni, The Conversation, 10 Mar. 2026
In astronauts who spent about a year aboard the International Space Station, some areas near the top of the brain moved upward by more than 2 millimeters, while the rest of the brain barely moved.
—Rachael Seidler, Space.com, 7 Mar. 2026
The Arabian and Eurasian plates continue to move toward each other at around 20 millimeters a year, sometimes triggering deadly earthquakes.
—Stephanie Pappas, Scientific American, 6 Mar. 2026
See All Example Sentences for millimeter
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Aamir Khollam, Interesting Engineering, 11 Mar. 2026
Over millions of years, metals in the surrounding seawater form coatings of iron and manganese oxides, with thicknesses ranging from a few millimeters to a few decimeters, depending on the age of the seamounts.
—Leonardo MacElloni, The Conversation, 10 Mar. 2026
In astronauts who spent about a year aboard the International Space Station, some areas near the top of the brain moved upward by more than 2 millimeters, while the rest of the brain barely moved.
—Rachael Seidler, Space.com, 7 Mar. 2026
The Arabian and Eurasian plates continue to move toward each other at around 20 millimeters a year, sometimes triggering deadly earthquakes.
—Stephanie Pappas, Scientific American, 6 Mar. 2026
See All Example Sentences for millimeter
Cite this Entry
“Millimeter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/millimeter. Accessed 15 Mar. 2026.
Copy CitationKids Definition
millimeter
noun
mil·li·me·ter
ˈmil-ə-ˌmēt-ər
: a measure of length equal to ¹⁄₁₀₀₀ meter see metric system table
Medical Definition
millimeter
noun
mil·li·me·ter
variants
or chiefly British millimetre
: one thousandth of a meter
—abbreviation mm
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