a signal that controls the traffic on a road, by means of red, orange and green lights that show when you must stop and when you can go

• 控制道路上交通的信号灯（a signal that controls the traffic on a road）
• 通过红色，橙色和绿色的灯（by means of red, orange and green lights ）
• 告诉你什么时候该停下来，什么时候该走（ that show when you must stop and when you can go）

人教精通版小学《英语》