Ouillage (Ouiller)

Ouillage refers to the "topping up" of wine in a barrel or vat. In the barrel in particular, part of the wine is absorbed by the wood, while the other part evaporates naturally. It's important to avoid a vacuum forming, as contact with oxygen could alter the wine—unless you're assuming or looking for a form of oxidation that gives it the famous taste of... Rancio. In this case, we speak of oxidative aging. In English, we often say "deliberate oxidation."