The Collaborative International Dictionary of English v.0.48:

Remorse \Re*morse"\ (r?*m?rs"), n. [OE. remors, OF. remors,F.
   remords, LL. remorsus, fr. L. remordere, remorsum, to bite
   again or back, to torment; pref. re- re- + mordere to bite.
   See Morsel.]
   1. The anguish, like gnawing pain, excited by a sense of
      guilt; compunction of conscience for a crime committed, or
      for the sins of one's past life. "Nero will be tainted
      with remorse." --Shak.
      [1913 Webster]

   2. Sympathetic sorrow; pity; compassion.
      [1913 Webster]

            Curse on the unpardoning prince, whom tears can draw
            To no remorse.                        --Dryden.
      [1913 Webster]

            But evermore it seem'd an easier thing
            At once without remorse to strike her dead.
                                                  --Tennyson.
      [1913 Webster]

   Syn: Compunction; regret; anguish; grief; compassion. See
        Compunction.
        [1913 Webster]

WordNet (r) 3.0 (2006):

remorse
    n 1: a feeling of deep regret (usually for some misdeed) [syn:
         compunction, remorse, self-reproach]