Definition of meridian

• a. - Being at, or pertaining to, midday; belonging to, or passing through, the highest point attained by the sun in his diurnal course.
• a. - Pertaining to the highest point or culmination; as, meridian splendor.
• a. - Midday; noon.
• a. - Hence: The highest point, as of success, prosperity, or the like; culmination.
• a. - A great circle of the sphere passing through the poles of the heavens and the zenith of a given place. It is crossed by the sun at midday.
• a. - A great circle on the surface of the earth, passing through the poles and any given place; also, the half of such a circle included between the poles.