/ Dictionary / Index O OAO: Meaning and Definition of Find definitions for: OAO Pronunciation: [key] Orbiting Astronomical Observatory: one of a series of scientific satellites that studied astronomical phenomena at ultraviolet and x-ray wavelengths. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. O and O OAP Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language