Wiktionary
n. (context chemistry English) Distillation under reduced pressure, and thus at a reduced temperature with less risk of thermal degradation
Wikipedia
Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure (usually less than atmospheric pressure) causing evaporation of the most volatile liquid(s) (those with the lowest boiling points). This distillation method works on the principle that boiling occurs when the vapor pressure of a liquid exceeds the ambient pressure. Vacuum distillation is used with or without heating the mixture.
Usage examples of "vacuum distillation".
The radiator and vacuum distillation sections of the water-purification-and-cooling system was in operation.
We calculate the overall cost to be less than five percent of conventional vacuum distillation or osmotic filter treatments.