A person secretly employed in espionage for a government
Synonyms:
  1. intelligence agent
  2. operative
  3. double-agent
  4. informer
  5. inside man
  6. intelligence officer
  7. mole
  8. scout
  9. snoop
  10. spy
  11. undercover agent
  12. undercover man
  13. cloak-and-dagger man