Definition of SPY

  1. (verb)catch sight of
  2. (verb)watch, observe, or inquire secretly
  3. (verb)catch sight of; to perceive with the eyes
  4. (verb)secretly collect sensitive or classified information; engage in espionage
  5. (noun)(military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors
  6. (noun)a secret watcher; someone who secretly watches other people