Ullage

[ʌlidʒ]

(noun.) the amount that a container (as a wine bottle or tank) lacks of being full.

Typist: Meg--From WordNet

(n.) The amount which a vessel, as a cask, of liquor lacks of being full; wantage; deficiency.

Typed by Elbert

n. the quantity a cask lacks of being full.—n. Ull′ing.

Edited by Davy