Term coined by parapsychologist Ian Stevenson to indicate
an uninvited entity or communicator at a séance, usually unknown
to medium or sitters.
Berger, Arthur S., and Joyce Berger. The Encyclopedia of
Parapsychology and Psychical Research. New York Paragon
Stevenson, Ian. A Communicator Unknown to Medium
and Sitter. Journal of the American Society for Psychical Research