niagara
n. uncountablen. a huge amount of water falling over a cliff, or any very large flow of something. It is most famous as the name of the giant waterfalls between the USA and Canada.
n. a massive waterfall or an overwhelming flood of something. When capitalised, it refers specifically to the Niagara Falls on the border of North America; used metaphorically to describe an unstoppable torrent.
A niagara of water poured from the broken pipe.
The speaker faced a niagara of questions from the angry crowd after the announcement.
The sudden collapse of the dam released a niagara of muddy water that swept through the valley, altering the landscape permanently within a matter of hours.
When referring to the specific geographic location, it is a proper noun and must be capitalised.