The Collaborative International Dictionary of English v.0.48:

Illuminate \Il*lu"mi*nate\, v. t. [imp. & p. p. Illuminated;
   p. pr. & vb. n. Illuminating.] [L. illuminatus, p. p. of
   illuminare; pref. il- in + luminare to enlighten, fr. lumen
   light. See Luminous, and cf. Illume, Illumine,
   Enlimn, Limn.]
   1. To make light; to throw light on; to supply with light,
      literally or figuratively; to brighten.
      [1913 Webster]

   2. To light up; to decorate with artificial lights, as a
      building or city, in token of rejoicing or respect.
      [1913 Webster]

   3. To adorn, as a book or page with borders, initial letters,
      or miniature pictures in colors and gold, as was done in
      manuscripts of the Middle Ages.
      [1913 Webster]

   4. To make plain or clear; to dispel the obscurity to by
      knowledge or reason; to explain; to elucidate; as, to
      illuminate a text, a problem, or a duty.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Illuminate \Il*lu"mi*nate\, v. i.
   To light up in token or rejoicing.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Illuminate \Il*lu"mi*nate\, a. [L. illuminatus, p. p.]
   Enlightened. --Bp. Hall.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Illuminate \Il*lu"mi*nate\, n.
   One who is enlightened; esp., a pretender to extraordinary
   light and knowledge.
   [1913 Webster]

WordNet (r) 3.0 (2006):

illuminate
    v 1: make lighter or brighter; "This lamp lightens the room a
         bit" [syn: light, illume, illumine, light up,
         illuminate]
    2: make free from confusion or ambiguity; make clear; "Could you
       clarify these remarks?"; "Clear up the question of who is at
       fault" [syn: clear, clear up, shed light on,
       crystallize, crystallise, crystalize, crystalise,
       straighten out, sort out, enlighten, illuminate,
       elucidate]
    3: add embellishments and paintings to (medieval manuscripts)

Moby Thesaurus II by Grady Ward, 1.0:

192 Moby Thesaurus words for "illuminate":
   account for, adorn, affect, allegorize, apply paint, beacon, bead,
   bedaub, bedizen, begild, bejewel, beribbon, besmear, bespangle,
   betoken, better, brandish, breathe, brighten, brighten up,
   bring forth, bring forward, bring into view, bring out,
   bring to notice, brush on paint, calcimine, clarify, clear,
   clear up, coat, color, complexion, construe, cover, crack, dab,
   dangle, daub, decipher, decorate, deep-dye, define, demonstrate,
   demythologize, develop, diamond, dip, disclose, display, distemper,
   divulge, double-dye, dramatize, dye, edify, elucidate, embellish,
   emblazon, embody, enact, enamel, engild, engrave, enlighten,
   ennoble, euhemerize, evidence, evince, exalt, exemplify, exhibit,
   explain, explain away, explicate, expose to view, exposit, expound,
   express, face, fast-dye, feather, figure, filigree, finish, fire,
   flag, flaunt, flood with light, floodlight, flounce, flourish,
   flower, fresco, garland, gem, gild, give reason for, give sign,
   give the meaning, give token, glaze, gloss, grain, highlight, hue,
   ignite, illume, illumine, illustrate, imbue, improve, incarnate,
   indicate, ingrain, interpret, irradiate, japan, jewel, kindle,
   lacquer, lay on color, light, light up, lighten, luminate,
   make clear, make plain, manifest, materialize, mature, mean,
   ornament, overshine, paint, parade, parget, perfect, perform,
   pigment, plume, polish, popularize, present, prime, produce,
   rationalize, refine, relume, relumine, represent, reveal, ribbon,
   roll out, set forth, shade, shadow, shed light upon, shellac,
   shine upon, show, show forth, show how, show the way, simplify,
   slop on paint, smear, solve, spangle, spell out, spotlight, stain,
   stipple, throw light upon, tinct, tincture, tinge, tinsel, tint,
   token, tone, trot out, undercoat, unfold, unlock, unravel, uplift,
   varnish, wash, wave, whitewash, wreathe