The rate at which the temperature of the atmosphere falls as altitude increases.

The environmental rate of decrease with height for an atmospheric variable or temperature: The atmospheric lapse rate is the rate of decrease with height and not simply the rate of change.

While most often applied to the Earth's atmosphere, the concept can be extended to any gravitationally supported ball of gas.

In other words, the atmospheric lapse rate involves the decrease of temperature with elevation in the atmosphere.

The "environmental lapse rate" is determined by the distribution of temperature in the vertical at a given time and place and should be carefully distinguished from the process lapse rate, which applies to an individual air parcel.