millimeter

/ˌˈmɪləˌmidər/

/ˈmɪlɪmitə/

Other forms: millimeters

A millimeter is a tiny unit of measurement. The thickness of a dime is a little more than a millimeter, and there are a thousand millimeters in a meter.

If you're using metric units to measure the length of something, you'll be dealing in meters and variations on meters, including millimeters. Look at a ruler that includes centimeters, the units of metric measurement that are closest in length to inches. The smallest units marked on the ruler are millimeters — there are ten of them in each centimeter. Although the word millimeter sounds like "million," it actually means "thousandth of a meter."

Definitions of millimeter

1. noun

   a metric unit of length equal to one thousandth of a meter
   synonyms: millimetre, mm

   type of:

   metric linear unit

   a linear unit of distance in metric terms