It was going to be deficit, but then, like Rooney, France, ‘let’s all laugh at Liverpool’ and, erm, deficit, I found it was being a bit overdone to death in the twittoscopia. On the same page (as deficit) in my dictionary is this: definiendum.
definiendum (pl: definienda) – a word, phrase, or symbol which is the subject of a definition, especially in a dictionary entry, or which is introduced into a logical system by being defined.
So, as far as I can tell, definiendum is the word that encompasses all other words. Amazing, and possibly better than 30 percent job cuts all round except at Eton.