/ Dictionary / Index O OSO: Meaning and Definition of Find definitions for: OSO Pronunciation: [key] — U.S. Aerospace. U.S. Aerospace. Orbiting Solar Observatory: one of a series of scientific satellites, launched between 1962 and 1975, that studied the sun at ultraviolet, x-ray, and gamma-ray wavelengths. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. osnaburg Osorno Related Content Daily Word Quiz: abstain Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language