Syllable division derived from spelling — this word is not in the pronouncing dictionary, so no phonetic transcription is shown rather than a guessed one.
magnetosphere is a noun meaning "the magnetic field of a planet; the volume around the planet in which charged particles are subject more to the planet's magnetic field than to the solar magnetic field". It carries one recorded sense.
the magnetic field of a planet; the volume around the planet in which charged particles are subject more to the planet's magnetic field than to the solar magnetic field
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for magnetosphere come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.