late Middle English: from Old French meridien, from Latin meridianum(neuter, used as a noun) noon, from mediusmiddle + diesday. The use in astronomy is due to the fact that the sun crosses a meridian at noon
英英释义行业释义网络释义
noun
1.an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator;
all points on the same meridian have the same longitude