Meridian (noun)

1. An imaginary great circle on the earth's surface, passing through the poles and any given point on the equator.
2. A line of longitude on a map or globe.
3. An astronomical term for the highest point reached by a celestial body in the sky.

Origin:

Late 16th century: from latin meridianus "of midday", from meridies "midday".

Examples:

1. The meridian of Greenwich, England, is defined as 0 degrees longitude.
2. The meridian marks the dividing line between the eastern and western hemispheres.
3. Solar eclipses occur when the moon passes across the sun's path along the meridian.
4. The city is located just west of the 75th meridian.
5. The meridian passing through the town was used to set the official time.