"spy" in the noun sense
1. spy, undercover agent
military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors
a secret watcher someone who secretly watches other people
"my spies tell me that you had a good time last night"
"spy" in the verb sense
1. descry, spot, espy, spy
catch sight of
2. spy, stag, snoop, sleuth
watch, observe, or inquire secretly
3. spy, sight
catch sight of to perceive with the eyes
"he caught sight of the king's men coming over the ridge"
secretly collect sensitive or classified information engage in espionage
"spy for the Russians"
Source: WordNet® (An amazing lexical database of English)
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