from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. The outermost shell of the atmosphere, between the mesosphere and outer space, where temperatures increase steadily with altitude.

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • n. layer of the Earth's atmosphere directly above the mesosphere and directly below the exosphere

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • n. the atmospheric layer between the mesosphere and the exosphere


thermo- + -sphere (Wiktionary)



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