danger signal

• n. 危险信号

例句

用作名词 (n.)

1. A red lamp is used as a danger signal.
   红灯用作危险信号。
2. The engine also began its whistle-calls of four parts, with which it signalled danger to important crossings.
   机车也开始在过重要的道口时，发出断续四响的汽笛声，作为危险信号。