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

Despite its fierce-sounding description, the animal measures nearly 6 millimeters in length — roughly the width of a standard pencil eraser. —Hanna Wickes, Charlotte Observer, 20 Feb. 2026

His boots were four millimeters over the standard. —Ryan Gaydos, FOXNews.com, 16 Feb. 2026

Never one to back down, Adamczyková went for it, diving feet-first into the line for every millimeter of a photo finish. —Brendan Quinn, New York Times, 13 Feb. 2026

In astronauts who spent about a year aboard the International Space Station, some areas near the top of the brain moved upward by more than 2 millimeters, while the rest of the brain barely moved. —Rachael Seidler, The Conversation, 11 Feb. 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