The Collaborative International Dictionary of English v.0.48:

Innocence \In"no*cence\, n. [F. innocence, L. innocentia. See
   Innocent.]
   1. The state or quality of being innocent; freedom from that
      which is harmful or infurious; harmlessness.
      [1913 Webster]

   2. The state or quality of being morally free from guilt or
      sin; purity of heart; blamelessness.
      [1913 Webster]

            The silence often of pure innocence
            Persuades when speaking fails.        --Shak.
      [1913 Webster]

            Banished from man's life his happiest life,
            Simplicity and spotless innocence!    --Milton.
      [1913 Webster]

   3. The state or quality of being not chargeable for, or
      guilty of, a particular crime or offense; as, the
      innocence of the prisoner was clearly shown.
      [1913 Webster]

   4. Simplicity or plainness, bordering on weakness or
      silliness; artlessness; ingenuousness. --Chaucer. Shak.

   Syn: Harmlessness; innocuousness; blamelessness; purity;
        sinlessness; guiltlessness.
        [1913 Webster]

WordNet (r) 3.0 (2006):

innocence
    n 1: the quality of innocent naivete [syn: artlessness,
         innocence, ingenuousness, naturalness]
    2: the state of being unsullied by sin or moral wrong; lacking a
       knowledge of evil [syn: purity, pureness, sinlessness,
       innocence, whiteness]
    3: a state or condition of being innocent of a specific crime or
       offense; "the trial established his innocence" [ant: guilt,
       guiltiness]