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

Snow fleas typically measure between 4 and 10 millimeters long, and have a 4-6 segment body with two antennae and six legs, reported the Lansing State Journal, part of the USA TODAY network. —Saleen Martin, USA Today, 22 Jan. 2026

The energetic 'snow flea' Snow fleas — or Hypogastruna nivicola of the order Collembola — are 4-10 millimeters long and have a 4-6 segment body with two anntenae and six legs. —Marina Johnson, Louisville Courier Journal, 22 Jan. 2026

Green Tea May Lower Blood Pressure A normal blood pressure is less than 120/80 millimeters of mercury (mmHg). —Sarah Bence, Verywell Health, 20 Jan. 2026

From 2012 to 2022 a research team collected observations of these unusual webs in Peru, the Philippines and Madagascar, focusing on about 300 individuals from the genus Cyclosa that are typically only a few millimeters long. —Gennaro Tomma, Scientific American, 19 Jan. 2026

Word History

Etymology

French millimètre, from milli- + mètre meter

First Known Use

1797, in the meaning defined above

Rhymes for millimeter

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

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