The Collaborative International Dictionary of English v.0.48:

Repentant \Re*pent"ant\ (-ant), a. [F. repentant.]
   1. Penitent; sorry for sin. --Chaucer.
      [1913 Webster]

            Thus they, in lowliest plight, repentant stood.
                                                  --Millton.
      [1913 Webster]

   2. Expressing or showing sorrow for sin; as, repentant tears;
      repentant ashes. "Repentant sighs and voluntary pains."
      --Pope.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Repentant \Re*pent"ant\, n.
   One who repents, especially one who repents of sin; a
   penitent.
   [1913 Webster]

WordNet (r) 3.0 (2006):

repentant
    adj 1: feeling or expressing remorse for misdeeds [syn:
           penitent, repentant] [ant: impenitent,
           unremorseful, unrepentant]

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "repentant":
   abject, apologetic, ascetic, ashamed, atoning, cleansing,
   compensational, compensatory, compunctious, contrite, embarrassed,
   expiatory, humble, humbled, lustral, lustrational, lustrative,
   melted, penitent, penitential, penitentiary, piacular,
   propitiatory, purgative, purgatorial, purifying, reclamatory,
   recompensing, redeeming, redemptive, redressing, regretful,
   remorseful, reparative, reparatory, repenting, restitutional,
   restitutive, restitutory, righting, rueful, satisfactional,
   sheepish, softened, sorry, squaring, touched