/ Dictionary / Index M milli-: Meaning and Definition of Find definitions for: milli- Pronunciation: [key] 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). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. millhouse milliammeter Related Content Daily Word Quiz: paradox Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language