phantom (
http://definr.com/phantom)
adj : something apparently sensed but having no physical reality;
"seemed to hear faint phantom bells"; "the amputee's
illusion of a phantom limb"
n 1: a ghostly appearing figure; "we were unprepared for the
apparition that confronted us" [syn:
apparition,
specter,
spectre]
2: something existing in perception only: "a ghostly apparition
at midnight" [syn:
apparition,
shadow]