*sig·nal¹/`sɪgnḷ; ˈsɪɡnəl/ n [C] 1 a sound, action, or event that gives information or tells someone to do something 信号，暗号: Wait for my signal. 等我的信号。 The result is a clear signal that voters are not happy. 选举结果是个明显的信号，说明选民不满意。 2 a series of light waves, sound waves etc that carry information to a radio, television etc 〔无线电、电视等的〕信号，讯号: broadcasting signals 广播信号 3 a piece of equipment that tells a train driver whether to go or stop 铁路信号