sleeper agent
spy who is placed in a target country or organization to act as a potential asset if activated and not to undertake an immediate mission
en-US/sˈlipɚ ˈeɪd͡ʒənt/
en-GB/ˈsliːpə æʒɒn/
spy who is placed in a target country or organization to act as a potential asset if activated and not to undertake an immediate mission