/ Dictionary / Index M medium octavo: Meaning and Definition of Find definitions for: me'dium octa'vo Pronunciation: [key] a size of book, about 6 × 9 in. (15 × 24 cm), untrimmed. Abbr.: medium 8vo Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. mediumistic medium of exchange Related Content Daily Word Quiz: tactful Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language