Definitions of spy

n (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
Margarete Gertrud Zelle
Dutch dancer who was executed by the French as a German spy in World War I (1876-1917)
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counterspy, mole
a spy who works against enemy espionage
double agent
a spy who works for two mutually antagonistic countries
espionage agent
someone employed to spy on another country or business competitor
foreign agent
a spy for a foreign country
someone who takes up a position surreptitiously for the purpose of espionage
a spy or saboteur or terrorist planted in an enemy country who lives there as a law-abiding citizen until activated by a prearranged signal
Type of:
intelligence agent, intelligence officer, operative, secret agent
a person secretly employed in espionage for a government

n a secret watcher; someone who secretly watches other people

“my spies tell me that you had a good time last night”
snoop, snooper
a spy who makes uninvited inquiries into the private affairs of others
shadow, shadower, tail
a spy employed to follow someone and report their movements
a secret listener to private conversations
Type of:
looker, spectator, viewer, watcher, witness
a close observer; someone who looks at something (such as an exhibition of some kind)

v watch, observe, or inquire secretly

sleuth, snoop, stag
Type of:
monitor, supervise
keep tabs on; keep an eye on; keep under surveillance

v catch sight of; to perceive with the eyes

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descry, espy, spot
catch sight of
detect, discover, find, notice, observe
discover or determine the existence, presence, or fact of
catch out, find out
trap; especially in an error or in a reprehensible act
detect some circumstance or entity automatically
find an instance of (a word or particular usage of a word)
discover traces of
observe as if with an eye
Type of:
comprehend, perceive
to become aware of through the senses

v catch sight of

descry, espy, spot
Type of:
catch sight of; to perceive with the eyes

v secretly collect sensitive or classified information; engage in espionage

spy for the Russians”
Type of:
enquire, inquire, investigate
conduct an inquiry or investigation of