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

Microplastics are plastic fragments smaller than 5 millimeters — about the size of a pencil eraser or smaller. — Tom Gavin, EverydayHealth.com, 15 July 2026

Cadence Design Systems and Synopsys are two of the largest manufacturers of chip design software, which helps to map billions of microscopic transistors onto a surface area of just a few millimeters. — Joseph Wilkins, CNBC, 13 July 2026

The mules have a short, 8-millimeter heel with extra padding for maximum support and come in four neutral shades. — Rachel Trujillo, PEOPLE, 13 July 2026

That cover is made of 10-millimeter-thick cotton quilted with a reflective casing that blocks heat from the sun instead of absorbing it. — Olivia Young, Travel + Leisure, 12 July 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