nautical mile

:  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: such asa :  a British unit equal to 6080 feet (1853.2 meters)b :  an international unit equal to exactly 1852 meters (6076.115 feet or 1.15 statute miles) used officially in the U.S. since July 1, 1954