/ˈsɪgnəl ||; ˈsɪgnḷ/noun[C] 1 a sign, action or sound that sends a particular message 信号；暗号: When I give (you) the signal, run! 我一发出信号，你就跑！
2 an event, action or fact that shows that sth exists or is likely to happen 标志；表示: The fall in unemployment is a clear signal that the economy is improving. 失业率下降明确标志着经济在改善。
3 a set of lights used to give information to train drivers 铁路信号灯
4 a series of radio waves, etc that are sent out or received （无线电波等传送的）信号:
a signal from a satellite 恒星信号
signal verb [I,T] (
signalling;signalled (
US 美)
signaling;signaled)
She was signalling wildly that something was wrong. 她拚命示意出了事。