/ɛksəˈsfɛrɪk/ (eks-uh-SFER-ik)

Definitions

1. adjective

relating to or denoting the outermost layer of a planet’s atmosphere, extending from the Karman line at about 100 km altitude to the outer limit of the atmosphere.

“The spacecraft had to withstand the harsh exospheric conditions of the upper atmosphere.”

2. noun

the exospheric region of a planet’s atmosphere.

“The exospheric layer is the least studied part of Earth’s atmosphere.”