JW Definition of "Apostate"
If you look up "apostasy" on Wikipedia, and scroll down, you will see a separate subsection for Jehovah's Witnesses.
In dictionaries, the word is usually defined along the lines of a renunciation of one's reliigion (or principles or cause etc), but most Christians, if they use it at all, tend to restrict the term to those who abandon faith in God altogether, not those who change religious denomination, or those who dispute individual teachings or leaders within a denomination.
JW's use lots of words and expressions in ways that normal people don't. I think the O.P makes a good point, in the JW mind "Apostate" is equivalent to Demon.
When an Elder, with another listening in, 'pnoned to accuse me of Apostasy, when he said the word, the fear was palpable, his voice dropped to a whisper as he said the word !
As I mentioned to a couple of Elders, Apostasy is standing apart from ones former beliefs, either religious or political, and they cannot accuse me of that now, having been gone for a decade I never subscribed to what they teach now, so could not leave it !
The will continue to use it as a word to engender fear, so that JW's stay off Sites like this, and therefore do not get to know Truth.
The Organizational view of apostasy is deliberately quite broad. However, as Shepherless mentioned ... apostasy is generally viewed as occurring when a person proclaims the complete abandonment of his faith for another (or none in some cases) ... where as a heretic is a person who proclaims his or her disagreement with a established church primary teaching and does not want to recant.