Plain English Meaning
When air that is already saturated rises, it cools more slowly than dry air does, because the moisture condensing into cloud droplets gives off heat that partly offsets the cooling.
Full Definition
The rate at which a parcel of saturated (cloud-forming) air cools as it rises, or warms as it descends, when no heat is exchanged with the surrounding air. Because condensation releases latent heat into the rising parcel, the cooling rate is slower than for dry air — typically around 2 to 3 °C per 1,000 feet, varying with temperature and moisture content.
Context Anchor
Seen in weather and atmospheric stability discussions, especially when comparing rising moist air with surrounding air to understand clouds, , and storm growth.