meridian
/məˈrɪdɪən; mə`rɪdɪən/ n
1 imaginary circle round the earth, passing through (a given place and) the North and South Poles 子午线; 经线
the Greenwich meridian, ie longitude 0, which passes through the North and South Poles and Greenwich, England 格林威治子午线.
2 highest point reached by the sun or other star, as viewed from a given point on the earth's surface 从地面观测太阳或其他星球到达的最高点.