storm cloud
noun
1- a heavy, dark rain cloud暴雨云, 雷雨云。
1.1
storm clouds
used in reference to a threatening or ominous state of affairs危险形势（或不祥）的预兆：the beginning of the decade saw storm clouds gathering over Europe.
在这个十年的开端, 欧洲就出现了不祥之兆。