Definition of "Ghost" :

noun: a mental representation of some haunting experience

"He looked like he had seen a ghost."

noun: a suggestion of some quality

"He detected a ghost of a smile on her face."

noun: the visible disembodied soul of a dead person

noun: a writer who gives the credit of authorship to someone else

verb: write for someone else

"How many books have you ghostwritten so far?."

verb: haunt like a ghost; pursue

verb: move like a ghost

"The masked men ghosted across the moonlit yard."