Ullage

ullage, which derives from the French ouillage, has had a variety of meanings and uses in the English-speaking wine trade. It can mean the process of evaporation of wine held in wooden containers such as a barrel. The head space left in the container is also called the ullage, or ‘ullage space’, and the wine in that state is said to be ‘on ullage’. The word ullage is also used for any space in a stoppered wine bottle not occupied by wine (see fill level). And ullage is also used as a verb so that a bottle or barrel not entirely full is said to be ‘ullaged’.