ullage > define
noun
- The amount that a container (as a wine bottle or tank) lacks of being full. .
by WordNet 3.0 © 2006 by Princeton University
(n.) The amount which a vessel, as a cask, of liquor lacks of being full; wantage; deficiency.
by Webster's Revised Unabridged Dictionary
ULLAGE is the empty space present when a shipping container is not full.