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

Measuring less than a millimeter thick, this sensor basically acts like a neuron in our brain, processing and keeping the information even after the original signal is gone. — Maryna Holovnova, New Atlas, 27 June 2026

Wednesday’s tremors occurred on the boundary between the Caribbean and South American plates, which have been slipping at a rate of around 20 millimeters per year. — Kasha Patel, CNN Money, 25 June 2026

In this area, the USGS estimates the Caribbean plate is moving eastward relative to the South American plate at a rate of about 20 millimeters per year (about three-quarters of an inch). — Evan Bush, NBC news, 25 June 2026

Last month, two research teams used the tech to make hundreds of thousands more connections per millimeter than were previously possible, setting new records. — Alex Music, IEEE Spectrum, 25 June 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