ghost

a mental representation of some haunting experience; "he looked like he had seen a ghost"; "it aroused specters from his past"

a writer who gives the credit of authorship to someone else

the visible disembodied soul of a dead person

a suggestion of some quality; "there was a touch of sarcasm in his tone"; "he detected a ghost of a smile on her face"

move like a ghost; "The masked men ghosted across the moonlit yard"

haunt like a ghost; pursue; "Fear of illness haunts her"

write for someone else; "How many books have you ghostwritten so far?"