Amount by which a cask falls short of being full

• Amount of liquid lost in shipping
• To capacity, lid off, time for the remaining liquid
• Amount needed to make a full cask
• Empty portion of a bottle
• Liquid amount lost in storage
• Liquid lost from a container

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 or headspace is the unfilled space in a container, particularly with a liquid.

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 ...