mean business
be serious 严肃的；正经的
When he said he was going to the library to study，he meant business．他说他要去图书馆学习，他确实是认真说的。
By sending their top people to meet our leaders at the summit conference，they really showed they meant business．在这次最高级会议上，他们派出了他们的首领同我们的领袖见面，这表明他们是郑重其事的。