Longman Dictionary of Contemporary English
Wiktionary
n. A large rain cloud, with potential to bring a storm.
WordNet
n. a heavy dark cloud presaging rain or a storm
Usage examples of "storm cloud".
The young woman cried out and twisted around to see the horsewife, her breath coming in gasps, her eyes wide as she stared at the storm cloud.
It was about half the size of the first apparition and appeared at first to be nothing more or less than a small ambulatory storm cloud, complete with fitful flickers of lightning and sharp little thunderclaps.
As always, it was swaddled in wisps of black fog, giving it the appearance of a lone storm cloud or a mirage.
It was, after all, in a storm cloud that he had first met her, and he smiled at the memory.
It took up half the sky, blotting out the sun like a giant storm cloud.
I began, shouting over my shoulder again, but was interrupted by the looming shape of a skimmer flying directly at us in the storm cloud.
Wind-tattered streamers of black whirled out from the heat-driven storm cloud and roiled under me like ebony rivers.