meridian

(meh-RID-ee-un) In traditional Chinese medicine, one of 20 channels that form a network through which qi (the body's vital energy) flows and that connect the body's acupuncture sites.

An imaginary line on the earth's surface passing through both geographic poles and through any given point on the planet, also called a line of longitude.

A line running vertically from the north pole to the south pole along which all locations have the same longitude. The Prime Meridian (0) runs through Greenwich, England. From the Prime Meridian, measures of longitude are negative to the west and positive to the east up to 180, halfway around the globe.