Definition of "Meridian" :

noun: an imaginary great circle on the surface of the earth passing through the north and south poles at right angles to the equator

"All points on the same meridian have the same longitude."

noun: a town in eastern Mississippi

noun: the highest level or degree attainable; the highest stage of development

adjective: being at the best stage of development

adjective: of or happening at noon

"Meridian hour."