a plant of the Eurasian genus Petasites with fragrant whitish or purple flowers, woolly stems, and leaves formerly used to wrap butter: family Asteraceae (composites)
butterbur in American English
(ˈbʌtərˌbɜr)
noun
any of several plants (genus Petasites) of the composite family, esp. a European plant (P. hybridus), with large, kidney-shaped leaves