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

Engineers must align all parts to millimeter-level tolerances during pre-assembly so the components fit accurately once placed in the reactor cavity. — Aman Tripathi, Interesting Engineering, 30 July 2026

Detectives quickly determined that Blake’s handgun was not the murder weapon, which turned out to be a Walther P38 9-millimeter pistol that had been dumped in the big commercial trash bin. — Los Angeles Times, 30 July 2026

But the breakout performance might be Imax’s 70-millimeter screenings. — Alex Harring, CNBC, 27 July 2026

The scan revealed a 14-millimeter tumor on the right side of Toby’s brain. — Toria Sheffield, PEOPLE, 25 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