adjective

1. of or at noon
2. of or passing through the highest point in the daily course of any celestial body
3. of or at the highest point of prosperity, splendor, power, etc.
4. of or along a meridian
5. Rare southern

Etymology: OFr meridien < L meridianus, of noon, southern < meridies, noon, the south < older medidies < medius, mid + dies, day: see deity

noun

1. Archaic the highest apparent point reached by a celestial body in its course
2. 1. the highest point of power, prosperity, splendor, etc.; zenith; apex
   2. the middle period of one's life, regarded as the highest point of health, vigor, etc.; prime
3. Obsolete noon
4. Astron. a great circle passing through the celestial poles, the observer's zenith and nadir, and the horizon's north and south points
   also called celestial meridian
5. Geog.
   1. a great circle of the earth passing through the geographical poles and any given point on the earth's surface
   2. either half of such a circle between the poles
   3. any of the lines of longitude running north and south on a globe or map, representing such a half circle
6. Archaic distinctive character as of a particular place