ullage

/ˈʌlɪdʒ/
noun
  1. The amount of liquid missing from a container that is not completely full, or the empty space left in a container (such as a bottle, barrel, or tank) after the liquid has been removed or settled.
    • The winemaker measured the ullage in each barrel to check for evaporation.
    • After the long voyage, the ship's fuel tanks showed significant ullage due to leakage.
    • The inspector noted the ullage in the oil drum and recorded it in the log.
  2. The process of measuring or accounting for the empty space in a container, especially in shipping or storage of liquids.
    • The crew performed ullage on all the cargo tanks before departure.
    • Ullage is an important step in ensuring accurate inventory of bulk liquids.
    • The technician completed the ullage and reported the results to the warehouse manager.
Antonyms