Definition of Spy

Verb: spy spI

Watch, observe, or inquire secretly
- stag, snoop, sleuth
Catch sight of; to perceive with the eyes
"he caught spy of the king's men coming over the ridge";
- sight, descry, spot, espy
Secretly collect sensitive or classified information; engage in espionage
"spy for the Russians"

Noun: spy spI

(military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors
- undercover agent
A secret watcher; someone who secretly watches other people
"my spies tell me that you had a good time last night"
A person secretly employed in espionage for a government
- secret agent, intelligence officer, intelligence agent, operative, spook