- [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
Synonyms: undercover agent
- [noun] a secret watcher; someone who secretly watches other people; "my spies tell me that you had a good time last night"
- [verb] catch sight of
Synonyms: descry, spot
- [verb] watch, observe, or inquire secretly
Synonyms: stag, snoop, sleuth
- [verb] secretly collect sensitive or classified information; engage in espionage; "spy for the Russians"