ullage
Concise Oxford English Dictionary © 2008 Oxford University Press:
ullage /ˈʌlɪdʒ/
▶noun
- 1 the amount by which a container falls short of being full.
- 2 loss of liquid by evaporation or leakage.
– origin ME: from Anglo-Norman Fr. ulliage, from OFr. euillier ‘fill up’, based on L. oculus ‘eye’ (with ref. to a container's bunghole).
'ullage' also found in these Oxford entries:

