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