Source : Webster's Revised Unabridged Dictionary (1913)

Radiant \Ra"di*ant\, a. (Physics)
   Emitted or transmitted by radiation; as, a radiant energy;
   radiant heat.

Radiant \Ra"di*ant\, n.
   1. (Opt.) The luminous point or object from which light
      emanates; also, a body radiating light brightly.

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

   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.

Radiant \Ra"di*ant\, 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; [U.S.] rays;
      radiating; radiate.

   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.

            Mark what radiant state she spreads.  --Milton.

   3. Beaming with vivacity and happiness; as, a radiant face.

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

   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.

   {Radiant energy} (Physics), energy given out or transmitted
      by radiation, as in the case of light and radiant heat.

   {Radiant 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.

Source : WordNet®

radiant
     adj : radiating or as if radiating light; "the beaming sun"; "the
           effulgent daffodils"; "a radiant sunrise"; "a refulgent
           sunset" [syn: {beaming}, {beamy}, {effulgent}, {refulgent}]