- Line of longitude running from pole to pole, on the Earth, another solid body or the celestial sphere
- noun an imaginary great circle on the Earth’s surface passing through the north and south geographic poles
- An imaginary great circle along the surface of the planet which passes through both geographic poles. All points along a given meridian have the same longitude, with the prime meridian passing through longitude 0°. Also, a great half-circle joining both geographic poles.
- An imaginary great circle along the surface of a celestial body which passes through both its geographic poles, or that joins them.
- noun in acupuncture and Chinese medicine, one of the pathways in the body along which its energy is believed to flow
Origin & History of “meridian”
Etymologically, meridian denotes the ‘middle of the day’. It comes via Old French from Latin merīdiānus, a derivative of merīdiēs ‘mid-day’. this was an alteration of an earlier medidiēs, a compound noun formed from medius ‘middle’ (source of English medium) and diēs ‘day’. The application of the word to a circle passing round the earth or the celestial sphere, which is an ancient one, comes from the notion of the sun crossing it at noon.