Source : Webster's Revised Unabridged Dictionary (1913)

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.