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]