Empty portion of a bottle

• Amount by which a cask falls short of being full
• Amount of liquid lost in shipping
• The amount that a container (as a wine bottle or tank) lacks of being full
• Unfilled part of a wine container
• Result of liquid loss in a cask
• To capacity, lid off, time for the remaining liquid
• Liquid amount lost in storage

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
Ullage \Ul"lage\ (?; 48), n. [OF. eullage, ovillage, the filling up of a cask, fr. ouillier, oillier, euillier, to fill a wine cask; properly, to add oil to prevent evaporation, as to a flask that is nearly full, fr. OF. oile oil. See Oil .] (Com.) The ...

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 ...

Wikipedia Word definitions in Wikipedia
Ullage (from the French ouillage ) is a winemaking term that has several meanings but most commonly refers to the headspace of air between wine and the top of the container holding the wine. It can also refer to the process of evaporation that creates the ...