Ghibelline UK /ˈɡɪbɪlaɪn/US /ˈɡɪbəlin/ noun1 •(historical) In the politics of medieval Italian city states, any member of a faction that supported the Holy Roman Emperor in a long struggle against the Guelphs and the Pope.More specifically, Fastello is said to address those Ghibellines who resided in the Valdarno area. — 2019 formsGhibellines