Reichstag Syllabification: (Reichs·tag)Pronunciation: /ˈrīksˌtäg, ˈrīKHs-/Definition of Reichstag the main legislature of the German state under the Second and Third Reichs. the building in which the Reichstag met. Origin:German, from Reichs 'of the empire' + Tag 'diet' (see diet2)Reichstag in other Oxford dictionaries Definition of Reichstag in the British & World English dictionary