The Collaborative International Dictionary of English v.0.48:

Luminous \Lu"mi*nous\, a. [L. luminosus, fr. lumen light: cf. F.
   lumineux. See Luminary, Illuminate.]
   [1913 Webster]
   1. Shining; emitting or reflecting light; brilliant; bright;
      as, the is a luminous body; a luminous color.
      [1913 Webster]

            Fire burneth wood, making it . . . luminous.
                                                  --Bacon.
      [1913 Webster]

            The mountains lift . . . their lofty and luminous
            heads.                                --Longfellow.
      [1913 Webster]

   2. Illuminated; full of light; bright; as, many candles made
      the room luminous.
      [1913 Webster]

            Up the staircase moved a luminous space in the
            darkness.                             --Longfellow.
      [1913 Webster]

   3. Enlightened; intelligent; also, clear; intelligible; as, a
      luminous mind. " Luminous eloquence." --Macaulay. " A
      luminous statement." --Brougham.
      [1913 Webster]

   Luminous paint, a paint made up with some phosphorescent
      substance, as sulphide of calcium, which after exposure to
      a strong light is luminous in the dark for a time.
      [1913 Webster]

   Syn: Lucid; clear; shining; perspicuous.
        [1913 Webster] -- Lu"mi*nous*ly, adv. --
        Lu"mi*nous*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

luminous
    adj 1: softly bright or radiant; "a house aglow with lights";
           "glowing embers"; "lambent tongues of flame"; "the lucent
           moon"; "a sky luminous with stars" [syn: aglow(p),
           lambent, lucent, luminous]

Moby Thesaurus II by Grady Ward, 1.0:

176 Moby Thesaurus words for "luminous":
   ablaze, acute, aglow, alight, all-knowing, all-powerful,
   all-seeing, all-wise, almighty, apprehensible, bathed with light,
   beaming, beamy, bespangled, blushing, boundless, bright,
   bright and sunny, brightened, brilliant, burning, candescent,
   candlelit, changeless, clean-cut, clear, clear as crystal,
   clear as day, clear-cut, clear-eyed, coherent, comprehensible,
   connected, consistent, creating, creative, crisp, crystal,
   crystal-clear, crystalline, dazzling, defined, definite, direct,
   discerning, distinct, effulgent, enlightened, eternal,
   eternally the same, everlasting, explicit, express, fathomable,
   firelit, fluorescent, flushing, fulgent, gaslit, gleaming, gleamy,
   glinting, glistening, glorious, glowing, good, graspable, hallowed,
   highest, holy, illuminant, illuminated, immortal, immutable,
   in a blaze, incandescent, incisive, infinite, intelligible,
   irradiate, irradiated, irradiative, just, keen, knowable, lambent,
   lamping, lamplit, lanternlit, light as day, lighted, lightened,
   limitless, limpid, lit, lit up, loud and clear, loving, lucent,
   lucid, luciferous, lucific, luciform, luminant, luminative,
   luminescent, luminiferous, luminificent, lustrous, majestic,
   making, merciful, moonlit, numinous, omnipotent, omnipresent,
   omniscient, one, orient, pellucid, penetrating, perceptive,
   percipient, permanent, perpetual, perspicacious, perspicuous,
   phosphorescent, plain, radiant, refulgent, resplendent, rutilant,
   rutilous, sacred, shaping, sharp, shimmering, shining, shiny,
   simple, sovereign, spangled, sparkling, specific, star-spangled,
   star-studded, starbright, starlike, starlit, starry,
   straightforward, streaming, studded, suffused, sunlit, sunny,
   sunshiny, supreme, timeless, tinseled, translucent, transparent,
   transpicuous, ubiquitous, unambiguous, unbounded, unchanging,
   unconfused, undefined, understandable, unequivocal, univocal,
   unlimited, unmistakable, well-defined