암행어사가 · 암행어사를
secret royal inspector
Example
암행어사는 몰래 지방을 다니며 수령들을 감시했어요.
Secret royal inspectors traveled the provinces in disguise, watching the magistrates.
Word parts
암 secret+행 go+어 royal+사 official
Literally 'royal official who travels in secret'.
Good to know
The famous cry 암행어사 출두요! means the inspector is revealing himself, as in The Tale of Chunhyang.