Merriam-Webster Collegiate Dictionary - meridian

 geographical name  1. city SW Idaho W of Boise population 34,919  2. city E central Mississippi population 39,968 MERIDIAN  noun  Etymology: Middle English, from Anglo-French meridien, from meridien of noon, from Latin ~us, from meridies noon, south, irregular from medius mid + dies day — more at mid, deity  Date: 14th century  1. archaic the hour of noon ; midday  2. a great circle of the celestial sphere passing through its poles and the zenith of a given place — see azimuth illustration  3. a high point  4.  a.  (1) a great circle on the surface of the earth passing through the poles  (2) the half of such a circle included between the poles  b. a representation of such a circle or half circle numbered for longitude on a map or globe — see longitude illustration  5. any of the pathways along which the body's vital energy flows according to the theory behind acupuncture  • ~ adjective