>The quantity of liquor contained in a cask partially filled and the capacity of the portion which is empty are termed respectively the wet and dry ullage.

well, imagine that... a word which is its own opposite!? hey jojo!!

but on a less serious note, here's what Norman Schur ("1000 Most Challenging Words") has to say: Ullage is used of a bottle of wine part of which has been lost by evaporation. In England, ullage was formerly used as a slang term for "dregs" and even more generally, "rubbish".
One might, then, refer to this whole thread as ullage.