meridian

noun

• 1a circle of constant longitude passing through a given place on the earth’s surface and the terrestrial poles.
• (also celestial meridian) Astronomy a circle passing through the celestial poles and the zenith of a given place on the earth’s surface.

• 2(in acupuncture and Chinese medicine) each of a set of pathways in the body along which vital energy is said to flow. There are twelve such pathways associated with specific organs.

adjective

• relating to or situated at a meridian:the meridian moon
• literary of noon.
• literary of the period of greatest splendor, vigor, etc..