one of the imaginary lines joining the north and south poles at right angles to the equator, designated by degrees of longitude from 0° at Greenwich to 180°
b.
the great circle running through both poles
prime meridian
2. astronomy
a.
the great circle on the celestial sphere passing through the north and south celestial poles and the zenith and nadir of the observer
b.
(as modifier)
a meridian instrument
3. Also called: meridian section mathematics
a section of a surface of revolution, such as a paraboloid, that contains the axis of revolution
4.
the peak; zenith
the meridian of his achievements
5.
(in acupuncture, etc) any of the channels through which vital energy is believed to circulate round the body
6. obsolete
noon
adjective
7.
along or relating to a meridian
8.
of or happening at noon
9.
relating to the peak of something
Word origin
C14: from Latin merīdiānus of midday, from merīdiēs midday, from mediusmid1 + diēs day