thermosphere noun. ['Ɵǝ:mǝsfɪǝ] E20.
[from THERMO- + -SPHERE.]
1. a. The part of the atmosphere below about 8 km in which air density is largely dependent on temperature. rare. Only in E20.
b. The part of the atmosphere between the mesopause and the height at which it ceases to have the properties of a continuous medium, characterized by an increase of temperature with height. M20.

2. The warmer upper part of the ocean. M20.

■ thermo'spheric adjective L20.

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