Pronunciation: (mâr'ē-an'u, mar'-, mâr"-, mar"-; Sp. mä"rē-ä'nä),[key] a group of 15 small islands in the Pacific, E of the Philippines: divided into Guam, a possession of the U.S., and the North Marianas, formally under U.S. trusteeship. 453 sq. mi. (1127 sq. km). Also called Mar"i•an'as. Formerly, Ladrone Islands, Ladrones. Cf. North Mariana Islands.