jackboot Syllabification: (jack·boot)Pronunciation: /ˈjakˌbo͞ot/Translate jackboot | into Italian Definition of jackboot noun a large leather military boot reaching to the knee. [in singular] used as a symbol of cruel or authoritarian behavior or rule:a country under the jackboot of colonialismDerivatives jackbooted adjective jackboot in other Oxford dictionaries Definition of jackboot in the British & World English dictionary