noun
: 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 ft. or 1853.2 meters — called also Admiralty mile
b. : a United States unit no longer in official use equal to 6080.20 ft. or 1853.248 meters
c. : an international unit equal to 6076.11549 ft. or 1852 meters used officially in the United States since July 1, 1959