topping; topping-up
A term that refers to adding wine to containers, such as oak barrels, to replace liquid that has evaporated. topping is necessary to ensure there’s no airspace (ullage) that would allow air contact with the wine (see oxidized). The French term for this procedure is ouillage.
The New Wine Lovers Companion, 2nd Edition, by Ron Herbst and Sharon Tyler Herbst. Copyright © (1) 2003, 1995 by Ron Herbst and Sharon Tyler Herbst. Reprinted by arrangement with Barron's Educational Series, Inc.