the name of two Italian explorers and navigators. John (circa 1450-circa 1498); Italian name Giovanni Caboto. An Italian in the service of England, he sailed from Bristol in 1497 in search of Asia, but in fact discovered the mainland of North America. Sebastian (circa 1475-circa 1557), son of John. It is thought that he accompanied his father on his voyage in 1497 and that he made further voyages after the latter’s death, most notably to explore the coast of Brazil and the Plate River in 1526.