geograafilist põhja- ja lõunapoolust ning vaatluskohta läbiva tasandi ja maaellipsoidi lõikejoon. Samal meridiaanil paiknevatel punktidel on ühine geograafiline pikkus.
the great circle (of the earth) which lies in the plane of the celestial meridian of a place, and which passes through the place and the poles; also often applied to that half of this circle that extends from pole to pole through the place. So named because the sun crosses it at noon. A terrestrial globe, or a map of the earth or part of it, has usually a number of meridians drawn upon it at convenient distances, marked with figures indicating their respective longitude or angular distance on a parallel from the first meridian, i.e. the meridian (in British maps that of Greenwich) conventionally determined to be of longitude 0°.
All waters of the Atlantic and Arctic Oceans and their dependent seas bounded by a line from the geographic North Pole along the meridian of 40°00' west longitude to the north coast of Greenland ...
