/ Dictionary / Index M magnetosphere: Meaning and Definition of Find definitions for: mag•ne•to•sphere Pronunciation: (mag-nē'tu-sfēr"), [key] — n. Astron. the outer region of the earth's ionosphere, where the earth's magnetic field controls the motion of charged particles, as in the Van Allen belts. Cf. such a region of another planet: Jupiter's magnetosphere. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: magnetosphere (Thesaurus) magnetosheath magnetostatics Related Content Daily Word Quiz: dissonant Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language