That temperature at which water vapour present in the atmosphere is just sufficient
to saturate it. When air is cooled below the dew point, the excess of water vapour
appears as tiny droplets or crystals of ice depending on the temperature of the air
mass. This term is also applicable to acid gases as in the problem of acid
corrosion and acid smut formation.
Source:
PAC, 1990, 62, 2167
(Glossary of atmospheric chemistry terms (Recommendations 1990))
on page 2184