The Collaborative International Dictionary of English v.0.48:

Enlightenment \En*light"en*ment\, n.
   1. Act of enlightening, or the state of being enlightened or
      instructed.
      [1913 Webster]

   2. same as Aufkl[aum]rung.
      [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

enlightenment
    n 1: education that results in understanding and the spread of
         knowledge [ant: unenlightenment]
    2: (Hinduism and Buddhism) the beatitude that transcends the
       cycle of reincarnation; characterized by the extinction of
       desire and suffering and individual consciousness [syn:
       nirvana, enlightenment]
    3: a movement in Europe from about 1650 until 1800 that
       advocated the use of reason and individualism instead of
       tradition and established doctrine; "the Enlightenment
       brought about many humanitarian reforms" [syn:
       Enlightenment, Age of Reason]

Moby Thesaurus II by Grady Ward, 1.0:

146 Moby Thesaurus words for "enlightenment":
   accomplishments, account, acculturation, acquaintance,
   acquisition of knowledge, acquisitions, allegorization,
   announcement, arc lighting, attainments, awakening,
   black and white, blue book, briefing, bulletin, catechization,
   chiaroscuro, civility, civilization, clarification, coaching,
   communication, communique, contrast, cracking, cultivation,
   culture, data, datum, debunking, decipherment, decoding,
   decorative lighting, demonstration, demythologization, didactics,
   direct lighting, direction, directory, disappointment,
   disenchantment, disillusion, disillusionment, dispatch,
   edification, editing, education, electric lighting, elucidation,
   emendation, enculturation, euhemerism, evidence, exegesis,
   exemplification, explanation, explication, exposition, expounding,
   facts, factual information, familiarization, festoon lighting,
   floodlighting, fluorescent lighting, gaslighting, gen,
   general information, glow lighting, guidance, guidebook, handout,
   hard information, highlights, illumination, illustration,
   incandescent lighting, incidental information, indirect lighting,
   info, information, instruction, intelligence, irradiation,
   knowledge, learning, liberal education, light, light and shade,
   lighting, mention, message, notice, notification,
   overhead lighting, pedagogics, pedagogy, polish, presentation,
   private teaching, programmed instruction, promotional material,
   proof, publication, publicity, radiation, rationale, reason,
   reeducation, refinement, release, report, return to reality,
   rude awakening, schooling, self-instruction, self-teaching,
   sidelight, simplification, socialization, solution, sophistication,
   spoon-feeding, spot lighting, stage lighting, statement,
   store of knowledge, strip lighting, teaching, the dope, the goods,
   the know, the scoop, tonality, transmission, tuition, tutelage,
   tutorage, tutoring, tutorship, undeception, unlocking, unspelling,
   white book, white paper, word