ullage
noun[CorU]
PRODUCTION,MEASURESuk/ˈʌlɪdʒ/usthespacein aclosedcontainerofliquidthat is notfilledby theliquid:
Mostwinesarebottledforimmediateconsumption, and the ullage should besmall.
Therequirementtodetermineullage beforebeginningoildeliveryappliesto all abovegroundstoragetanks.