cloud

in atmospheric chemistry
https://doi.org/10.1351/goldbook.C01107
An @A00176@ of the atmosphere which is dense enough to be perceptible to the eye. Usually refers to an assembly of water droplet aerosols suspended in the atmosphere, although dust clouds are also recognized.
Source:
PAC, 1990, 62, 2167. (Glossary of atmospheric chemistry terms (Recommendations 1990)) on page 2180 [Terms] [Paper]