/ˈʌndərkʌvər spaɪ/ – Phrase
Definition: gián điệp có vỏ bọc tốt.
A more thorough explanation: An undercover spy is an individual who secretly gathers information or conducts surveillance on behalf of a government agency or organization, typically for the purpose of obtaining intelligence or monitoring activities of interest.
Example: The undercover spy infiltrated the criminal organization to gather evidence for the prosecution.