noun (n)

• a mental representation of some haunting experience(noun.cognition)

  Example:
  It aroused specters from his past.
  

  Synonym:
  ghost, shade, spectre, spook, wraith
  

  source: wordnet30
• a ghostly appearing figure(noun.person)

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

  source: wordnet30
• Something preternaturally visible; an apparition; a ghost; a phantom.(noun)

  source: webster1913