The Collaborative International Dictionary
Diurnal \Di*ur"nal\, a. [L. diurnalis, fr. dies day. See Deity, and cf. Journal.]
Relating to the daytime; belonging to the period of daylight, distinguished from the night; -- opposed to nocturnal; as, diurnal heat; diurnal hours.
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Daily; recurring every day; performed in a day; going through its changes in a day; constituting the measure of a day; as, a diurnal fever; a diurnal task; diurnal aberration, or diurnal parallax; the diurnal revolution of the earth.
Ere twice the horses of the sun shall bring Their fiery torcher his diurnal ring.
--Shak. (Bot.) Opening during the day, and closing at night; -- said of flowers or leaves.
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(Zo["o]l.) Active by day; -- applied especially to the eagles and hawks among raptorial birds, and to butterflies (Diurna) among insects.
Diurnal aberration (Anat.), the aberration of light arising from the effect of the earth's rotation upon the apparent direction of motion of light.
Diurnal arc, the arc described by the sun during the daytime or while above the horizon; hence, the arc described by the moon or a star from rising to setting.
Diurnal circle, the apparent circle described by a celestial body in consequence of the earth's rotation.
Diurnal motion of the earth, the motion of the earth upon its axis which is described in twenty-four hours.
Diurnal motion of a heavenly body, that apparent motion of the heavenly body which is due to the earth's diurnal motion.
Diurnal parallax. See under Parallax.
Diurnal revolution of a planet, the motion of the planet upon its own axis which constitutes one complete revolution.
Syn: See Daily.
Wiktionary
n. (context astrology English) the path followed by a planet, point, or degree from its rising point to its setting point.
Wikipedia
Usage examples of "diurnal arc".
On the contrary, the engineer inclined it towards the south, that is to say, in the direction of the coast opposite to the sun, for it must not be forgotten that the settlers in Lincoln Island, as the island was situated in the Southern Hemisphere, saw the radiant planet describe its diurnal arc above the northern, and not above the southern horizon.
On the contrary, the engineer inclined it toward the south, that is to say, in the direction of the coast opposite to the sun, for it must not be forgotten that the settlers in Lincoln Island, as the island was situated in the Southern Hemisphere, saw the radiant planet describe its diurnal arc above the northern, and not above the southern horizon.
The weather men were still racking their brains when the sun's diurnal arc eased southward past the equator and spring officially began in Mesklin's southern hemisphere.
But once or twice, large shadows, veiling the sun, which described its diurnal arc through an extremely clear sky, indicated that a thick cloud of smoke passed between its disc and the island.
On this day, the sun which had risen at twenty minutes to six, set at forty minutes past five, having traced its diurnal arc for eleven hours above the horizon.