ghost

(noun) a mental representation of some haunting experience. Synonyms: shade, spook, wraith, specter, spectre. Examples: "He looked like he had seen a ghost." "It aroused specters from his past."

(noun) a writer who gives the credit of authorship to someone else. Synonyms: ghostwriter.

(noun) the visible disembodied soul of a dead person.

(noun) a suggestion of some quality. Synonyms: touch, trace. Examples: "There was a touch of sarcasm in his tone." "He detected a ghost of a smile on her face."

(verb) move like a ghost. Example: "The masked men ghosted across the moonlit yard."

(verb) haunt like a ghost; pursue. Synonyms: haunt, obsess. Example: "Fear of illness haunts her."

(verb) write for someone else. Synonyms: ghostwrite. Example: "How many books have you ghostwritten so far?."