n. 信号( signal的名词复数 ); （无线电或电视所传送的）讯号; 标志; （尤指铁路和公路上的）指示灯

v. 发信号, 用信号传达, 用信号通讯( signal的第三人称单数 ); 发暗号; 示意

n any nonverbal action or gesture that encodes a message

n any incitement to action

n an electric quantity (voltage or current or field strength) whose modulation represents coded information about the source from which it comes

v communicate silently and non-verbally by signals or signs

v be a signal for or a symptom of