(or Urushi, or Mackenzie Island), coral atoll in the Federated States of Micronesia, in the western Pacific Ocean; islets have a total land area of 1.75 sq mi (4.5 sq km); probably sighted by the Portuguese in 1526; undisturbed by Europeans until visited by a British naval vessel in 1791; site of Japanese seaplane base during World War II; captured by U.S. forces in 1944, and served as a large U.S. naval base for the rest of the war; inhabitants are probably partly Polynesian and speak a distinctive dialect; pop. 710.