Undertake/ˌʌndərˈteɪk/ Definition 1 of 4Pro Tip 1/2Serious Promise Using 'undertake' often suggests a serious, formal commitment. He undertook to serve his country with honor. Pro Tip 2/2Long-term Responsibility 'Undertake' implies a commitment that usually extends over time. She undertook the long-term task of writing her memoir.