spy

noun
  1. A person who secretly collects information about an enemy or competitor, typically for military, political, or commercial purposes. noun
    The spy was caught trying to infiltrate the enemy's headquarters.
    During the Cold War, many spies operated covertly in foreign countries.
  2. To secretly gather information about someone or something, often for espionage or intelligence purposes. verb
    He was hired to spy on the rival company's activities.
    The agents were tasked to spy on the suspected terrorists.