/ Dictionary / Index P plasmasphere: Meaning and Definition of Find definitions for: plas•ma•sphere Pronunciation: (plaz'mu-sfēr"), [key] — n. Astron. a region of cool plasma surrounding the earth, extending 8000–25,000 mi. (13,000–40,000 km) into space, and bounded by the plasmapause. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. plasmasol plasma thromboplastic component Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language