interventionist Syllabification: (in·ter·ven·tion·ist)Pronunciation: /ˌintərˈvenSHənist/Definition of interventionist adjective favoring intervention, especially by a government in its domestic economy or by one country in the affairs of another. noun a person who favors government intervention. Derivatives interventionismPronunciation: /-ˌnizəm/ noun interventionist in other Oxford dictionaries Definition of interventionist in the British & World English dictionary