In the most simple terms, an 'apostate' is someone who voices any disagreement with whatever current interpretation of doctrine made by the Governing Body or publicly denounces wrongdoing amongst the JW's.
You don't have to be a disfellowshipped or dissociated JW to be labelled an 'apostate'. I know, because that is happening with me at the moment.
Unfavorable media reports about the Jehovah's Witnesses, even if they are of independent origin, are considered 'apostate'. The reasoning behind it is that Satan, the original apostate, is instigating those reports.
If you stick to the Watchtower publications and the Bible alone to point out inconsistencies or perceived errors and doctrinal flip-flops in JW doctrine, your motivations for doing so will be questioned, and you'll likely be labelled an apostate.
If you harbor doubts or disagree or simply can't wrap your head around a JW teaching or change in doctrine, that's OK, as long as you keep 'listening and obeying' the leadership and 'wait on Jehovah' to have your doubts enlightened. But if you share those doubts with others in the congregation other than Elders, and if you insist on not keeping your mouth shut, you risk being accused of 'causing divisions' or 'attempting to create a sect' and you'll be labelled an apostate, and dealt judicially with.
Eden