noun
plural spies
[count] a person who tries secretly to get information about a country or organization for another country or organization
someone who secretly watches the movement or actions of other people
verb
spies; spied; spying
[no obj] :to try secretly to get information about a country, organization, etc. :to act as a spy
[+ obj] :to see or notice (someone or something)
spy on
[phrasal verb]
spy on (someone or something) :to watch (someone) secretly
spy out
[phrasal verb]
spy (something) out or spy out (something) :to notice, find, or learn about (something) by looking often in a secret way
spy out the land chiefly Brit :to find or get more information about a situation secretly and before making a decision