potential temperature

https://doi.org/10.1351/goldbook.P04787
The temperature that a dry air parcel would have if lowered or raised adiabatically to a level of 1000 mbar pressure (or other arbitrary standard pressure).
Source:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2207 (https://doi.org/10.1351/pac199062112167)