noun

• A river (the Niagara River) which flows from Lake Erie, over Niagara Falls into Lake Ontario; the geographical region of the United States and Canada in proximity to this river.
• A ghost town in British Columbia, Canada.
• A regional municipality on the Niagara Peninsula, southern Ontario, Canada, colloquially known as the Niagara Region.
• A ghost town in Western Australia.
• A town in New York.
• A city and village in North Dakota.
• A city and town in Wisconsin.
• (metonymically) The Niagara Falls.
• (figuratively) A flood, torrent, or outpouring, especially one of massive proportions.
• A Niagara grape.