mesosphere

noun

1. (in the classification of the earth’s atmosphere by chemical properties) the region between the ionosphere and the exosphere, extending from about 250–650 miles (400–1050 km) above the surface of the earth.
2. (in the classification of the earth’s atmosphere by thermal properties) the region between the stratosphere and the thermosphere, extending from about 20–50 miles (32–80 km) above the surface of the earth.

noun

1. the atmospheric layer lying between the stratosphere and the thermosphere, characterized by a rapid decrease in temperature with height
2. the solid part of the earth’s mantle lying between the asthenosphere and the core

n.1950, from meso- + second element in atmosphere.

1. The region of the Earth’s atmosphere lying above the stratosphere and below the thermosphere, from a height of about 50 km (31 mi) to about 80 km (50 mi) above the Earth’s surface. In the mesosphere temperatures decrease with increasing altitude due to the decreasing absorption of ultraviolet radiation from the Sun. At the top of this region temperatures are around -95°C (-135.4°F). Most of the meteors that enter Earth’s atmosphere burn up while passing through the mesosphere. See also exosphere stratosphere thermosphere troposphere. See illustration at atmosphere.