Definitions of apparition:

• noun:   an act of appearing or becoming visible unexpectedly

  Example: "Natives were amazed at the apparition of this white stanger"

• noun:   something existing in perception only

  Example: "A ghostly apparition at midnight"

• noun:   the appearance of a ghostlike figure

  Example: "I was recalled to the present by the apparition of a frightening specter"

• noun:   a ghostly appearing figure

  Example: "We were unprepared for the apparition that confronted us"