The meaning of this dream varies depending on what happened. If the ghost simply appeared in your dream, it is an omen of general good luck; however, if you were frightened by it or it spoke to you, it is a warning that some powerful pressure could be brought to bear on you to join in a scheme or activity that is against your principles. Resist the temptation with all the strength you can muster, and if necessary get help from a trusted friend or adviser.