NAUTICAL MILE

[nautical mile] n (1834): any of various units of distance used for sea and air navigation based on the length of a minute of arc of a great circle of the earth and differing because the earth is not a perfect sphere: as a: a British unit equal to 6080 feet (1853.2 meters) b: an international unit equal to 6076.115 feet (1852 meters) used officially in the U.S. since July 1, 1959