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 13 millimeters wide, this belt is extra thick. —Renee Cherry, SELF, 2 July 2025

Nearly invisible to the naked eye at just 0.2 millimeters long, oak leaf itch mites commonly feed on larvae of oak gall midge flies that live on pin oak leaves. —Alex Perry, The Enquirer, 1 July 2025

The 42 refers to the size of the front lens in millimeters. —Scott Gilbertson, Wired News, 25 June 2025

Size also varies with the average kidney stone being around 5 to 6 millimeters in diameter, which is about the size of a pencil eraser. —Daryl Austin, USA Today, 23 June 2025

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