From Glossary of Meteorology
(Also called irreversible moist-adiabatic process.) A moist-adiabatic process in which the liquid water that condenses is assumed to be removed as soon as it is formed, by idealized instantaneous precipitation.
The pseudoadiabatic process is only defined for expansion, since a parcel that is compressed after such expansion will follow the dry-adiabatic lapse rate. A process similar to pseudoadiabatic descent can occur, however, if drizzle is evaporated into a relatively slow downdraft.