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

The resulting metal sheet was then cut into circles that can be incorporated into dials and inserted in the watches’ 43-millimeter cases at the brand’s studio in Liège, Belgium. —Oscar Holland, CNN Money, 6 Nov. 2025

Recycling with a purpose The students made the bikes’ frames from two-inch (55-millimeter) carbon-fiber tubes that once served as structural components in Airbus A380. —Georgina Jedikovska, Interesting Engineering, 5 Nov. 2025

Microplastics are pieces of plastic smaller than five millimeters. —Matt Fuchs, Time, 5 Nov. 2025

The teacher, then 25, alleged Parker ignored multiple warnings that the boy might have brought a 9-millimeter handgun to school. —Sarah Rumpf-Whitten, FOXNews.com, 4 Nov. 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