The Collaborative International Dictionary of English v.0.48:

Repentance \Re*pent"ance\ (r[-e]*p[e^]nt"ans), n. [F.
   repentance.]
   The act of repenting, or the state of being penitent; sorrow
   for what one has done or omitted to do; especially,
   contrition for sin. --Chaucer.
   [1913 Webster]

         Godly sorrow worketh repentance to salvation. --2. Cor.
                                                  vii. 20.
   [1913 Webster]

         Repentance is a change of mind, or a conversion from
         sin to God.                              --Hammond.
   [1913 Webster]

         Repentance is the relinquishment of any practice from
         the conviction that it has offended God. Sorrow, fear,
         and anxiety are properly not parts, but adjuncts, of
         repentance; yet they are too closely connected with it
         to be easily separated.                  --Rambler.
   [1913 Webster]

   Syn: Contrition; regret; penitence; contriteness;
        compunction. See Contrition.
        [1913 Webster]

WordNet (r) 3.0 (2006):

repentance
    n 1: remorse for your past conduct [syn: repentance,
         penitence, penance]

Moby Thesaurus II by Grady Ward, 1.0:

34 Moby Thesaurus words for "repentance":
   Day of Atonement, Yom Kippur, abject apology, apology, asceticism,
   attrition, change of heart, cold purgatorial fires, compunction,
   contriteness, contrition, deathbed repentance, fasting,
   flagellation, hair shirt, heartfelt apology, lustration,
   maceration, mea culpa, mortification, penance, penitence,
   penitential act, penitential exercise, penitently, purgation,
   purgatory, reformation, remorse, rue, ruth, sackcloth and ashes,
   saeta, wearing a hairshirt



Easton's 1897 Bible Dictionary:

Repentance
   There are three Greek words used in the New Testament to denote
   repentance. (1.) The verb _metamelomai_ is used of a change of
   mind, such as to produce regret or even remorse on account of
   sin, but not necessarily a change of heart. This word is used
   with reference to the repentance of Judas (Matt. 27:3).

     (2.) Metanoeo, meaning to change one's mind and purpose, as
   the result of after knowledge. This verb, with (3) the cognate
   noun _metanoia_, is used of true repentance, a change of mind
   and purpose and life, to which remission of sin is promised.

     Evangelical repentance consists of (1) a true sense of one's
   own guilt and sinfulness; (2) an apprehension of God's mercy in
   Christ; (3) an actual hatred of sin (Ps. 119:128; Job 42:5, 6; 2
   Cor. 7:10) and turning from it to God; and (4) a persistent
   endeavour after a holy life in a walking with God in the way of
   his commandments.

     The true penitent is conscious of guilt (Ps. 51:4, 9), of
   pollution (51:5, 7, 10), and of helplessness (51:11; 109:21,
   22). Thus he apprehends himself to be just what God has always
   seen him to be and declares him to be. But repentance
   comprehends not only such a sense of sin, but also an
   apprehension of mercy, without which there can be no true
   repentance (Ps. 51:1; 130:4).


The Devil's Dictionary (1881-1906):

REPENTANCE, n.  The faithful attendant and follower of Punishment.  It
is usually manifest in a degree of reformation that is not
inconsistent with continuity of sin.

    Desirous to avoid the pains of Hell,
    You will repent and join the Church, Parnell?
    How needless! -- Nick will keep you off the coals
    And add you to the woes of other souls.
                                                         Jomater Abemy