mean business
US /miːn ˈbɪz.nɪs/
UK /miːn ˈbɪz.nɪs/

1.
진심이다, 진지하다
to be serious and determined about what one is doing or saying
:
•
When the boss walked in with that look on his face, we knew he meant business.
상사가 그런 표정으로 들어왔을 때, 우리는 그가 진심이라는 것을 알았다.
•
The new security measures show that the company means business about protecting its data.
새로운 보안 조치들은 회사가 데이터 보호에 진심이라는 것을 보여준다.