phantom

Adjective

• something apparently sensed but having no physical reality
  • seemed to hear faint phantom bells
    
  • the amputee's illusion of a phantom limb
    

Noun

• something existing in perception only
  • a ghostly apparition at midnight
    

• a ghostly appearing figure
  • we were unprepared for the apparition that confronted us
    

Related words

• Synonyms: 
  apparition , phantasm , phantasma , fantasm , shadow , specter , spectre