Definitions for ionosphereaɪˈɒn əˌsfɪər
Random House Webster's College Dictionary
the region of the earth's atmosphere between the stratosphere and the exosphere, consisting of several ionized layers and extending from about 50 to 250 mi. (80 to 400 km) above the surface of the earth.
the outer region of the Earth's atmosphere; contains a high concentration of free electrons
The part of the Earth's atmosphere beginning at an altitude of about 50 kilometers (31 miles) and extending outward 500 kilometers (310 miles) or more.
The similar region of the atmosphere of another planet.
Dictionary of Military and Associated Terms
That part of the atmosphere, extending from about 70 to 500 kilometers, in which ions and free electrons exist in sufficient quantities to reflect electromagnetic waves.