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
signalverb [I,T] (signalling;signalled (US 美) signaling;signaled)
She was signalling wildly that something was wrong.她拚命示意出了事。