/ Dictionary / Index U upper atmosphere: Meaning and Definition of Find definitions for: up'per at'mosphere Pronunciation: [key] — Meteorol. Meteorol. the portion of the atmosphere above the troposphere. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. upper arm Upper Austria Related Content Daily Word Quiz: fidelity Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language