What is "radiant point"

Radiant \Ra"di*ant\ (r[=a]"d[i^]*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; resembling 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.

6. (Physics) Emitted or transmitted by radiation; as, a radiant energy; radiant heat.

   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.