1The side of a planet or moon facing away from the sun and therefore in darkness.
〔天文〕阴暗面（行星或卫星因背对太阳而处于黑暗中的那一面）
Example sentencesExamples
The first satellite, Geotail, was launched in 1992 by Japan's Institute of Space and Astronautical Science to study the distant reaches of Earth's magnetic tail, the region downwind on the nightside of Earth.
Much of the time, those energetic particles trickle in through the rear flanks of Earth's magnetic tail - on the nightside - and near the polar regions.
The disk is Earth with its nightside facing the Moon.
2US mass nounActivities that take place during the night.
〈主美〉夜间世界；夜生活
nightside was the province of the professional criminals
Definition of nightside in US English:
nightside
nounˈnītsīd
1The side of a planet or moon facing away from the sun and therefore in darkness.
〔天文〕阴暗面（行星或卫星因背对太阳而处于黑暗中的那一面）
Example sentencesExamples
Much of the time, those energetic particles trickle in through the rear flanks of Earth's magnetic tail - on the nightside - and near the polar regions.
The disk is Earth with its nightside facing the Moon.
The first satellite, Geotail, was launched in 1992 by Japan's Institute of Space and Astronautical Science to study the distant reaches of Earth's magnetic tail, the region downwind on the nightside of Earth.
2US The world at night; activities that take place during the night.
〈主美〉夜间世界；夜生活
nightside was the province of the professional criminals