Exosphere

noun

noun ·Rare ·Advanced level

Definitions

Noun
  1. 1
    the uppermost layer of a planet's atmosphere
  2. 2
    the outermost atmospheric layer wordnet
  3. 3
    an extremely thin atmosphere, as on Saturn's moon Dione

    ""Scientists weren't even sure Dione would be big enough to hang on to an exosphere" ('Cassini Detects Hint of Fresh Air at Dione', , JPL, Mar. 02, 2012)"

Synonyms

All synonyms
exoatmosphere

Example

More examples

"The exosphere is the outermost layer of our atmosphere."

Etymology

From exo- + -sphere.

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Data sourced from Wiktionary, WordNet, CMU, and other open linguistic databases. Updated March 2026.