/ Dictionary / Index M meso-: Meaning and Definition of Find definitions for: meso- Pronunciation: [key] a combining form meaning “middle,” used in the formation of compound words: mesocephalic. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mesne lord Mesoamerica Related Content Daily Word Quiz: philtrum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language