foreboding; foregleam; omen; portent; sign; indication; [医] aura
ill omen
不祥的先兆
an omen of success
成功的先兆
indications of an impending earthquake
地震的先兆
portents of war
战争的先兆
It is said to be an omen of misfortune.
那被认为是一种不幸的先兆。
Black clouds are an unmistakable sign of coming rain.
乌云是下雨的明显先兆。