Thundercloud

Full definition of thundercloud

Noun

1. a large, dark cloud, usually a cumulonimbus, charged with electricity and producing thunder and lightning; a stormcloud
2. (by extension) something menacing and broodingAs the ominous thunderclouds of war gather over the Middle East, countries like France and Russia have threatened to use their veto in the United Nations to thwart immediate U.S. military force against Iraq. - http://www.faluninfo.net/displayAnArticle.asp?ID=7103