from Greek ἀδιάϐατος (adiabatos), which means «impassable»
→ done without total energy loss or gain
It is a humidification which is done by evaporating the free water surface, by supplying sensible energy from the air.
The air is cooled and humidified: it has lost sensible energy and gained latent energy, the total energy has remained equal.
In this process, the air is active and exchanges its sensible energy with the water (usually saturation is never reached unless there is an aftercooling).
Steam is produced at the free surface of the water by the supply of sensible energy from the air.