[1] : The Collaborative International Dictionary of English v.0.48

radiant \ra"diant\ r=a"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; 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
see also:
radius ray radiant energy radiant heat radiant point radiant 

[2] : WordNet (r) 2.0

radiant energy
     n : energy that is transmitted in the form of electromagnetic
         radiation; energy that exists in the absence of matter

[3] : Moby Thesaurus II by Grady Ward, 1.0

31 moby thesaurus words for "radiant energy":
   contamination, curiage, decontamination, emanation, fallout,
   half-life, highlight, illumination, irradiance, irradiancy,
   irradiation, light, light source, luminous energy,
   natural radioactivity, nuclear radiation, photosensitivity,
   radiance, radiancy, radiation, radioactive radiation,
   radioactivity, radiocarbon dating, radiolucency, radiopacity,
   radiosensibility, radiosensitivity, saturation point, sidelight,
   specific activity, visible radiation

Radiant Energy >> R Words
Radiant Energy, definition of term: Radiant Energy
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Radiant >> R Words
Radiant, definition of term: Radiant
radiant_pag1.html

Energy >> E Words
Energy, definition of term: Energy
energy_pag1.html

Solar Energy >> S Words
Solar Energy, definition of term: Solar Energy
solar+energy_pag1.html

Nuclear Energy >> N Words
Nuclear Energy, definition of term: Nuclear Energy
nuclear+energy_pag1.html

Kinetic Energy >> K Words
Kinetic Energy, definition of term: Kinetic Energy
kinetic+energy_pag1.html

Chemical Energy >> C Words
Chemical Energy, definition of term: Chemical Energy
chemical+energy_pag1.html

Heat Energy >> H Words
Heat Energy, definition of term: Heat Energy
heat+energy_pag1.html

Atomic Energy >> A Words
Atomic Energy, definition of term: Atomic Energy
atomic+energy_pag1.html

Mental Energy >> M Words
Mental Energy, definition of term: Mental Energy
mental+energy_pag1.html