millimeter

noun

mil·​li·​me·​ter ˈmi-lə-ˌmē-tər How to pronounce millimeter (audio)
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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
Measuring between 1 and 5 millimeters, the insects feed on human blood. — Jessica Mekles, FOXNews.com, 17 Oct. 2026 The researchers believe the design rules could eventually support robots just a few millimeters wide, since the snapping behavior depends on the rod’s geometry. — New Atlas, 16 Oct. 2026 Trudy was on track to become a major hurricane on Friday, bringing rainfall of 4 to 8 inches (101 to 203 millimeters) through the weekend across Colima and Jalisco states, the center said. — ABC News, 15 Oct. 2026 Microplastics are usually defined as particles smaller than five millimeters, while the minimum cutoff varies between 100 and 1,000 nanometers. — Jacek Krywko, ArsTechnica, 15 Oct. 2026 See All Example Sentences for millimeter

Word History

Etymology

French millimètre, from milli- + mètre meter

First Known Use

1797, in the meaning defined above

Time Traveler
The first known use of millimeter was in 1797

Rhymes for millimeter

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Browse Nearby Words

millime
millimeter
millimetric
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Cite this Entry

“Millimeter.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/millimeter. Accessed 20 Oct. 2026.

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Kids Definition

millimeter

noun
mil·​li·​me·​ter ˈmil-ə-ˌmēt-ər How to pronounce millimeter (audio)
: 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
ˈmil-ə-ˌmēt-ər How to pronounce millimeter (audio)
: one thousandth of a meter
—abbreviation mm
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