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

1.
是認真的, 不是開玩笑的
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.
當老闆帶著那種表情走進來時,我們知道他是認真的。
•
The new security measures show that the company means business about protecting its data.
新的安全措施表明公司是認真的,要保護其數據。