water vapor

noun

1. a dispersion, in air, of molecules of water, especially as produced by evaporation at ambient temperatures rather than by boiling.

water vapor

1. Water in its gaseous state, especially in the atmosphere and at a temperature below the boiling point. Water vapor in the atmosphere serves as the raw material for cloud and rain formation. It also helps regulate the Earth's temperature by reflecting and scattering radiation from the Sun and by absorbing the Earth's infrared radiation.

2. See also vapor

Word History and Origins

Origin of water vapor¹

First recorded in 1875–80