spy

1. (espionage) A person who secretly watches and examines the actions of other individuals or organizations and gathers information on them (usually to gain an advantage).Examples: "The dead leap at the throat, destroy The meaning of the day; dark forms Have scaled your walls, and spies betray Old secrets to amorphous swarms."; "Even without hovering drones, a lurking assassin, a thumping score and a denouement, the real-life story of Edward Snowden, a rogue spy on the run, could be straight out of the cinema. But, as with Hollywood, the subplots and exotic locations may distract from the real message: America’s discomfort and its foes’ glee."Synonyms: espy, intelligencer

2. (American football) A defensive player assigned to cover an offensive backfield player man-to-man when they are expected to engage in a running play, but the offensive player does not run with the ball immediately.