a U.S. trust territory in the Pacific Ocean, comprising the Mariana, Marshall and Caroline Islands: approved by the United Nations 1947; since 1976 constituents of the trusteeship have established or moved toward self-government. 133,732; 717 sq. mi. (1857 sq. km). Cf. Belau, Marshall Islands, Micronesia (def. 2), Northern Mariana Islands.