noun

an apparition of a dead person which is believed to appear or become manifest to the living, typically as a nebulous image.

the building is haunted by the ghost of a monk

spectre,phantom,wraith,spirit,soul,shadow,presence,vision,apparition,hallucination,bodach,Doppelgänger,duppy,spook,phantasm,shade,revenant,visitant,wight,eidolon,manes,lemures

verb

act as ghostwriter of (a work).

his memoirs were smoothly ghosted by a journalist