THUNDERCLOUD
cumulonimbus, cumulonimbus cloud, thundercloud
(noun) a dark cloud of great vertical extent charged with electricity; associated with thunderstorms
Source: WordNet® 3.1
Etymology
Noun
thundercloud (plural thunderclouds)
A large, dark cloud, usually a cumulonimbus, charged with electricity and producing thunder and lightning; a stormcloud
(by extension, figurative) Something menacing and brooding.
Source: Wiktionary
Thun"der*cloud`, n.
Definition: A cloud charged with electricity, and producing lightning and
thunder.
Source: Webster’s Unabridged Dictionary 1913 Edition