Main Entry: me·rid·i·an

Pronunciation: \mə-ˈri-dē-ən\

Function: noun

Etymology: Middle English, from Anglo-French meridien, from meridien of noon, from Latin meridianus, 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

— meridian adjective