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

Test for real-time surgery Hibbert’s brain tumor measured about 11 millimeters and sat in his pituitary gland. — Aamir Khollam, Interesting Engineering, 27 Aug. 2026

The nodules in those early cases ranged from 4 to 10 millimeters, and were the peripheral, hard-to-reach kind where conventional biopsy tools most often fall short. — Geri Stengel, Forbes.com, 21 Aug. 2026

After 15 years of experiments, Schumm’s group ended up with a recipe for solid calcium fluoride crystals, doped with little impurities of thorium 229, that looked like transparent millimeter-sized cubes. — Jacek Krywko, Scientific American, 20 Aug. 2026

Rakholia estimated the width of Kelce’s ring as being slightly smaller, putting it 5 or 6 millimeters wide. — Pete Grathoff, Kansas City Star, 19 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