Longman Dictionary of Contemporary English - spy

~1 n someone whose job it is to find out secret information about another country, organization, or group  (a British spy in World War II | a spy film) ~2 v 1 to secretly collect information about an enemy country or an organization you are competing against + on  (He was charged with spying on top-secret naval bases.) 2 spy on sb to watch someone secretly  (Jean's always spying on the neighbours.) 3 especially literary to suddenly see someone or something, especially after searching for them  (Ellen suddenly spied her friend in the crowd.) spy sth out phr v 1 to secretly find out information about something 2 spy out the land to secretly find out more information about a situation before deciding what to do