meridian
noun [ C ] uk/məˈrɪd.i.ən/ us/məˈrɪd.i.ən/
子午线，经线
an imaginary line between the North Pole and the South Pole, drawn on maps to help to show the position of a place
The prime meridian of longitude is in Greenwich, London. 本初子午线位于伦敦南部的格林尼治。