Rochester Syllabification: (Roch·es·ter)Pronunciation: /ˈräCHəstər, ˈräˌCHes-/Definition of Rochester 1an industrial city in southeastern Minnesota, home to the Mayo Clinic that was established in 1889; population 100,413 (est. 2008). 2a city in southeastern New Hampshire, northwest of Dover; population 30,654 (est. 2008). 3a city in northwestern New York, on Lake Ontario; population 206,886 (est. 2008). Rochester in other Oxford dictionaries Definition of Rochester in the British & World English dictionary