specter

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

(noun) a ghostly appearing figure. Synonyms: apparition, phantom, phantasm, phantasma, fantasm, spectre. Example: "We were unprepared for the apparition that confronted us."