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:

illuminated \illuminated\ adj. [p. p. of illuminate.]
   1. rendered luminous by rays of light striking and
      reflecting; -- used especially of illumination by
      artificial light.

   Syn: lighted.
        [PJC]

   2. Adorned with pictorial or graphical designs, 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; as, an illuminated manuscript.
      [1913 Webster]

WordNet (r) 3.0 (2006):

illuminated
    adj 1: provided with artificial light; "illuminated
           advertising"; "looked up at the lighted windows"; "a
           brightly lit room"; "a well-lighted stairwell" [syn:
           illuminated, lighted, lit, well-lighted]