The layer of air near the earth is cooler than an overlying layer WordNet 3.0 & Open English WordNet

In meteorology, an inversion is a deviation from the normal change of an atmospheric property with altitude. Wikipedia

Air temperature increasing with height Wikipedia Disambiguation

A layer within which an atmospheric property is inverted, i.e., its change is deviated from the normal pattern Wikipedia Disambiguation

Deviation from the normal change of an atmospheric property with altitude Wikidata

A weather phenomenon where the temperature in the atmosphere rises with increasing altitude. OmegaWiki

An increase of air temperature with increase in altitude (the ground being colder than the surrounding air). When an inversion exists, there are no convection currents and wind speeds are below 5 knots. The atmosphere is stable and normally is considered the most favorable state for ground release of chemical agents. Wiktionary