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

Industry fire-rating tables show that a solid brick wall only about 150 millimeters thick can withstand four hours of standard fire exposure. — Giorgia Giardina, The Conversation, 13 Aug. 2026

Not too close together – about 5 millimeters (1/4 inch) apart. — Mary Walrath-Holdridge, USA Today, 11 Aug. 2026

In order for a brain scan of the proper fidelity to be produced, the dogs must spend a minimum of six minutes in the machine, moving less than three millimeters in any direction. — Jeffrey Kluger, Time, 10 Aug. 2026

Then comes the ash and, sandwiched inside and just above it, two green films a few hundredths of a millimeter thick. — Jacek Krywko, ArsTechnica, 9 Aug. 2026

Word History

Etymology

French millimètre, from milli- + mètre meter

First Known Use

1797, in the meaning defined above

Rhymes for millimeter

• amphitheater
• bolometer
• centimeter
• centimetre
• decimeter
• ergometer
• expositor
• gasometer
• gravimeter
• hexameter
• manometer
• milliliter

Kids 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

ˈmil-ə-ˌmēt-ər 

: one thousandth of a meter

—abbreviation mm