The Collaborative International Dictionary of English v.0.48:

Excuse \Ex*cuse"\, v. t. [imp. & p. p. Excused; p. pr. & vb.
   n. Excusing.] [OE. escusen, cusen, OF. escuser, excuser, F.
   excuser, fr. L. excusare; ex out + causa cause, causari to
   plead. See Cause.]
   1. To free from accusation, or the imputation of fault or
      blame; to clear from guilt; to release from a charge; to
      justify by extenuating a fault; to exculpate; to absolve;
      to acquit.
      [1913 Webster]

            A man's persuasion that a thing is duty, will not
            excuse him from guilt in practicing it, if really
            and indeed it be against Gog's law.   --Abp. Sharp.
      [1913 Webster]

   2. To pardon, as a fault; to forgive entirely, or to admit to
      be little censurable, and to overlook; as, we excuse
      irregular conduct, when extraordinary circumstances appear
      to justify it.
      [1913 Webster]

            I must excuse what can not be amended. --Shak.
      [1913 Webster]

   3. To regard with indulgence; to view leniently or to
      overlook; to pardon.
      [1913 Webster]

            And in our own (excuse some courtly stains.)
            No whiter page than Addison remains.  --Pope.
      [1913 Webster]

   4. To free from an impending obligation or duty; hence, to
      disengage; to dispense with; to release by favor; also, to
      remit by favor; not to exact; as, to excuse a forfeiture.
      [1913 Webster]

            I pray thee have me excused.          --xiv. 19.
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   5. To relieve of an imputation by apology or defense; to make
      apology for as not seriously evil; to ask pardon or
      indulgence for.
      [1913 Webster]

            Think ye that we excuse ourselves to you? --2 Cor.
                                                  xii. 19.

   Syn: To vindicate; exculpate; absolve; acquit.

   Usage: - To Pardon, Excuse, Forgive. A superior pardons
          as an act of mercy or generosity; either a superior or
          an equal excuses. A crime, great fault, or a grave
          offence, as one against law or morals, may be
          pardoned; a small fault, such as a failure in social
          or conventional obligations, slight omissions or
          neglects may be excused. Forgive relates to offenses
          against one's self, and punishment foregone; as, to
          forgive injuries or one who has injured us; to pardon
          grave offenses, crimes, and criminals; to excuse an
          act of forgetfulness, an unintentional offense. Pardon
          is also a word of courtesy employed in the sense of
          excuse.
          [1913 Webster]

WordNet (r) 3.0 (2006):

excused
    adj 1: granted exemption; "one of the excused jurors planned to
           write a book"

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "excused":
   absolved, acquitted, blotted, canceled, chartered, condoned,
   disregarded, excepted, exculpated, exempt, exempted, exonerated,
   favored, forgiven, forgotten, immune, indulged, irresponsible,
   let off, licensed, overlooked, pardoned, permitted, privileged,
   redeemed, released, remitted, reprieved, shriven, spared,
   unaccountable, unanswerable, unavenged, uncondemned, unliable,
   unresented, unrevenged, unsubject, wiped away