明岗暗哨 míng gǎng àn shào

DEFINITIONS

  1. both covert and undercover (officers) keeping watch (idiom)

CHARACTERS

明 míng
HSK 1
bright, light, brilliant; clear
岗 gǎng
HSK 6
post; position
暗 àn
HSK 5
dark; obscure; in secret, covert
哨 shào
HSK 6
whistle, blow whistle; chirp