Ghosting is when you are dead and give information of the game to the people who are still alive.
For example player X died very early in the game and is spectating another player who is already bhopping through the map, after the deaths tried to kill him (activating the most traps) the player finaly dies. But then the other players are comming and are waiting infront of a trap, so player X decides to say: “Yo, this trap is already activated!”. And that would be ghosting.