Ghosting is a form of cheating which is not allowed. It is very easy to do and most people do not even realize that they are breaking the rules. Ghosting is when there are 2 or more people and they tell each other who the traitors are if one of them is the traitor or if they die say who killed them and then spectate and see who is doing traitorous deeds. Ghosting is frowned upon just like RDM and will consist in a ban on any server
The word ghosting is a reference to the fact you are dead, but still telling alive people who the traitors are like a ghost might talk to the living.