Definition of subatmospheric in US English:

subatmospheric

adjective

  • 1Geology. Taking place or existing in contact with the overlying atmosphere; subaerial.

  • 2Chiefly Medicine and Engineering. Of pressure: less than that of the atmosphere (at sea level under normal conditions).

Origin

Mid 19th century; earliest use found in Quarterly Journal of the Geological Society of London. From sub- + atmospheric.

Pronunciation

subatmospheric

/ˌsʌbatməsˈfɛrɪk/