step in
1．walk in走进
Would you mind stepping in for a moment？进来坐一会好吗？
The clerk stepped in and asked for Mr．Black．办事员走进来要找布莱克先生。
2．intervene either to help or hinder插进来（帮助或阻止）；干预
If the government does not step in，there will be no trains on Monday．政府要是不干预的话，星期一将没有任何火车。
The police are reluctant to step in．警察不愿插手干预。
Father stepped in and forbade me to go campimg．父亲进来干预不准我去野营。