Longman Dictionary of Contemporary English - phantasy

phantom ~ n literary 1 a frightening and unclear image, especially of a dead person; ghost1 (1): ~ horseman/hound/ship etc  (The phantom hound loomed suddenly out of the mist.) 2 something that exists only in your imagination  (the phantoms that troubled his dreams) 3 humorous used to describe an unknown person that you blame for something annoying  (The phantom pen stealer strikes again!)