Pronunciation: (is"tän-bOOl', -tan-; is'tän-bool", -tan-; Turk. is-täm'bool),[key] —n. a port in NW Turkey, on both sides of the Bosporus: built by Constantine I on the site of ancient Byzantium; capital of the Eastern Roman Empire and of the Ottoman Empire; capital removed to Ankara 1923. 5,494,900. Also,Stambul,Stamboul.Formerly ( a.d. 330–1930), Constantinople.