spy
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
Synonymsundercover agenta secret watcher; someone who secretly watches other people
“my spies tell me that you had a good time last night”
verb
catch sight of
watch, observe, or inquire secretly
catch sight of; to perceive with the eyes
“he caught sight of the king's men coming over the ridge”
Synonymssightsecretly collect sensitive or classified information; engage in espionage
“spy for the Russians”
Source: WordNet 3.1, Princeton University
