noun (n)

• a ghostly appearing figure(noun.person)

  Synonym:
  apparition, fantasm, phantasma, phantom, specter, spectre
  

  source: wordnet30
• something existing in perception only(noun.cognition)

  Synonym:
  apparition, fantasm, phantasma, phantom, shadow
  

  source: wordnet30
• An image formed by the mind, and supposed to be real or material; a shadowy or airy appearance; sometimes, an optical illusion; a phantom; a dream.(noun)

  source: webster1913