Amount needed to make a full cask

• Liquid amount lost in storage
• Amount of liquid lost in shipping
• Result of liquid loss in a cask
• Unfilled part of a wine container
• Amount by which a cask falls short of being full
• Amount lacking to make a full cask

Wiktionary Word definitions in Wiktionary
n. 1 In a wine bottle, the empty space between the cork and the top of the wine. 2 In a cask or barrel, the empty space, occupied by air, that is created by not completely filling the cask or barrel 3 The topping-up of such a barrel with fresh wine 4 In ...

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
"amount by which a cask or bottle falls short of being full," late 15c., from Anglo-French ulliage (early 14c.), Anglo-Latin oliagium (late 13c.), Old French ouillage , from ouiller "to fill up (a barrel) to the bung," literally "to fill to the eye," from ...

WordNet Word definitions in WordNet
n. the amount that a container (as a wine bottle or tank) lacks of being full

Wikipedia Word definitions in Wikipedia
Ullage or headspace is the unfilled space in a container, particularly with a liquid.