KasselPronunciation: /ˈkas(ə)l/Definition of Kassel a city in central Germany, in Hesse; population 193,500 (est. 2006). It was the capital of the kingdom of Westphalia (1807–13) and of the Prussian province of Hesse-Nassau (1866–1944). Kassel in other Oxford dictionaries Definition of Kassel in the US English dictionary