1. a combining form meaning “thousand” (millipede): in the metric system, used in the names of units equal to one thousandth of the given base unit (millimeter).

Origin of milli-

<French <Latin, combining form of mille thousand

Words Nearby milli- Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use milli- in a sentence

  • N er fr Gretti at segja; hann lt skamt hǫggva milli, ar til er jǫtunninn d. Gekk Grettir innar eptir hellinum.

    Beowulf | R. W. Chambers
  • The leader scowled at him, and some words were interchanged, but it ended in Milli being sent for.

  • Milli was an experienced swimmer, for the undersea folk enjoyed the privilege of a large indoor pool.

  • George and Milli then took up again the problem of saving the outer earth from the threatened invasion.

  • Silently Hakin and Abbot sprang upon the guard and throttled him; then released Milli.

British Dictionary definitions for milli-


  1. denoting 10 –3: millimetre Symbol: m

Origin of milli-

from French, from Latin mille thousand, this meaning being maintained in words borrowed from Latin (millipede)

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for milli-


  1. A prefix that means “one thousandth,” as in millimeter, one thousandth of a meter.

The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.