- noun a person involved in extremely covert operations (e.g. spying, special forces, etc)
- noun a black person. The reference is either an ironic one to the subjects’ black colour (as opposed to the white of spectres) or to their ‘haunting’ of certain locations.
- noun a spy, secret agent. This usage may be a simple reference to unseen ‘ghosts’ or may derive from the fact that many World War II agents were recruited from the Yale secret society, the ‘Skull and Bones’.