/ Dictionary / Index O open diapason: Meaning and Definition of Find definitions for: o'pen diapa'son. Pronunciation: [key] See under(def. 4). Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. open dating open die Related Content Daily Word Quiz: blithesome Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language