What is "vasto"

The Città del Vasto or Vasto (from the Greek Ἱστόνιον, Latin Histonium) is a town and comune on the Adriatic coast of the Province of Chieti in southern Abruzzo, Italy. It was also called in the Middle Ages as Guastaymonis or Il Vasto d'Ammone and also Waste d'Aimone. Renamed Istonio under the Fascist Rule, it took the current name of Vasto in 1944. In the local dialect it is called Lu Uas'te, that is Il Vasto.