/ Dictionary / Index O open union: Meaning and Definition of Find definitions for: o'pen un'ion Pronunciation: [key] a labor union that does not impose rigid restrictions on the admission of new members. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. open trailer open universe Related Content Daily Word Quiz: arboreal Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language