밀약이 · 밀약을
secret agreement, secret pact
Example
두 나라 사이에 밀약이 있었다는 사실이 드러났습니다.
It came to light that there had been a secret pact between the two countries.
Word parts
밀 secret+약 promise
Literally 'secret promise'.
Good to know
Pronounced [미략]; 밀약을 맺다 = to make a secret pact.