That said to be possessed by someone who is obsessed with something or only able to think of one thing.
Something apparently seen, heard, or sensed, but having no physical reality; an image that appears only in the mind; an illusion or delusion.
A ghost or apparition.
A placeholder for a pair of players when there are an odd number of pairs playing.
A test object. A test phantom is an object that reproduces the characteristics of human tissue.
Illusive.
Fictitious or nonexistent.