/ Dictionary / Index M middle-sized: Meaning and Definition of Find definitions for: mid•dle-sized Pronunciation: (mid'l-sīzd"), [key] — adj. medium-sized. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Middlesex Middle States Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language