A mirage, especially one in which the viewer sees castles. The phrase is an Italian translation of "Morgan le Fay," alluding to the character in the Arthurian legend. In the 19th century, a mirage attributed to le Fay's sorcery took place in Italy's Strait of Messina. A: "Do you see that castle ahead?" B: "No, so I think you're seeing a Fata Morgana."