say it: nahy-A-gruh
niagara is a noun meaning "waterfall in Canada is the Horseshoe Falls; in the United States it is the American Falls". It carries 2 recorded senses.
waterfall in Canada is the Horseshoe Falls; in the United States it is the American Falls
a river flowing from Lake Erie into Lake Ontario; forms boundary between Ontario and New York
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for niagara come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.