Entry 1 sense Webster, 1913 Masterwort · Mas·ter·wort · IPA /ˈmɑːstəwəːt/ 01 n. A tall and coarse European umbelliferous plant (Peucedanum Ostruthium, formerly Imperatoria). 1. A tall and coarse European umbelliferous plant (Peucedanum Ostruthium, formerly Imperatoria).(Bot.)