radian

n. [ From Radius. ] (Math.) An arc of a circle which is equal to the radius, or the angle measured by such an arc. [ 1913 Webster ]

{ } n. The quality of being radiant; brilliancy; effulgence; vivid brightness; as, the radiance of the sun. [ 1913 Webster ]

Girt with omnipotence, with radiance crowned. Milton. [ 1913 Webster ]

What radiancy of glory,
What light beyond compare ! Neale. [ 1913 Webster ]

Syn. -- Luster; brilliancy; splendor; glare; glitter. [ 1913 Webster ]

a. [ L. radians, -antis, p. pr. of radiare to emit rays or beams, fr. radius ray: cf. F. radiant. See Radius, Ray a divergent line. ] 1. Emitting or proceeding as from a center; resembling rays; radiating; radiate. [ 1913 Webster ]

2. Especially, emitting or darting rays of light or heat; issuing in beams or rays; beaming with brightness; emitting a vivid light or splendor; as, the radiant sun. [ 1913 Webster ]

Mark what radiant state she spreads. Milton. [ 1913 Webster ]

3. Beaming with vivacity and happiness; as, a radiant face. [ 1913 Webster ]

4. (Her.) Giving off rays; -- said of a bearing; as, the sun radiant; a crown radiant. [ 1913 Webster ]

5. (Bot.) Having a raylike appearance, as the large marginal flowers of certain umbelliferous plants; -- said also of the cluster which has such marginal flowers. [ 1913 Webster ]

6. (Physics) Emitted or transmitted by radiation; as, a radiant energy; radiant heat. [ Webster 1913 Suppl. ]

Radiant energy (Physics), energy given out or transmitted by radiation, as in the case of light and radiant heat. --
Radiant heat, heat proceeding in right lines, or directly from the heated body, after the manner of light, in distinction from heat conducted or carried by intervening media. --
Radiant point. (Astron.) See Radiant, n., 3. [ 1913 Webster ]

n. 1. (Opt.) The luminous point or object from which light emanates; also, a body radiating light brightly. [ 1913 Webster ]

2. (Geom.) A straight line proceeding from a given point, or fixed pole, about which it is conceived to revolve. [ 1913 Webster ]

3. (Astron.) The point in the heavens at which the apparent paths of shooting stars meet, when traced backward, or whence they appear to radiate. [ 1913 Webster ]

. (Mach.) A semiradial engine. See Radial engine, above. [ Webster 1913 Suppl. ]