What is the meaning of ghost?

noun

• A mental representation of some haunting experience.
  • usage: "he looked like he had seen a ghost"; "it aroused specters from his past"
  • synonyms: shade, spook, wraith, specter, spectre
• A writer who gives the credit of authorship to someone else.
  • synonyms: ghostwriter
• The visible disembodied soul of a dead person.
• A suggestion of some quality.
  • usage: "there was a touch of sarcasm in his tone"; "he detected a ghost of a smile on her face"
  • synonyms: touch, trace

verb

• Move like a ghost.
  • usage: "The masked men ghosted across the moonlit yard"
• Haunt like a ghost; pursue.
  • usage: "Fear of illness haunts her"
  • synonyms: haunt, obsess
• Write for someone else.
  • usage: "How many books have you ghostwritten so far"
  • synonyms: ghostwrite