secret agent 
noun
A spy acting for a country.At the same time, they were, and still are, fascinated by the exploits of secret agents and counterspies....
- For the longest time, we were used to our spies being secret agents.
- Did I cut the figure of an imposing secret agent of the intelligence field then?
Synonyms
spy, agent, double agent, counterspy, field agent, undercover agent, operative, plant, infiltrator, mole
North American informal spook
archaic intelligencer
- water stop
- water stream
- water stress
- water strider
- water-swallow
- water system
- water table
- water tablet
- water tabling
- water-target
- water taxi
- water telescope
- water therapy
- water thermometer
- water thief
- waterthrush
- water thyme
- water tick
- water tiger
- watertight
- watertight compartment
- watertightness
- water toad
- water toll
- water toothpick