Jerusalem artichoke
noun
Je·ru·sa·lem artichoke jə-ˈrü-s(ə-)ləm- 
-ˈrüz-ləm-,
-ˈrü-zə-
: a perennial sunflower (Helianthus tuberosus) of the U.S. and Canada widely cultivated for its tubers that are used as a vegetable and as a livestock feed
also : its tubers
Word History
Etymology
Jerusalem by folk etymology from Italian girasole girasole
First Known Use
1639, in the meaning defined above