What does "phantom" mean?

Phantom: That which has only an apparent existence; an apparition; a specter; a phantasm; a sprite; an airy spirit; an ideal image. Strange phantoms rising as the mists arise. Pope. She was a phantom of delight. Wordsworth. Phantom ship. See Flying Dutchman, under Flying. -- Phantom tumor (Med.), a swelling, especially of the abdomen, due to muscular spasm, accumulation of flatus, etc., simulating an actual tumor in appearance, but disappearing upon the administration of an anæsthetic.