spook

1 a person who tries secretly to obtain information for one country in the territory of another usually unfriendly country Russia recalled its spooks after the collapse of the Soviet Union Synonyms agent, asset, emissary, intelligencer, mole, operative, spy, undercoverRelated Words courier; counterspy, double agent, sleeper; infiltrator, informer, stool pigeon; spymaster, superspy

2 the soul of a dead person thought of especially as appearing to living people Halloween is the night when spooks and goblins are said to roam abroad Synonyms apparition, bogey (also bogie or bogy), familiar spirit, hant [dialect], haunt [chiefly dialect], materialization, phantasm (also fantasm), phantom, poltergeist, shade, shadow, specter (or spectre), spirit, ghost, sprite, vision, visitant, wraithRelated Words angel, daimon, familiar, genie, genius, jinni (or jinn also djinni or djinn), shaitan; double, doppelgänger (or doppelganger), fetch; lemures, manes; incubus, lamia, succubus, vampire, zombie (also zombi); cacodemon, demon (or daemon), devil, fiend, ghoul, imp