The Collaborative International Dictionary of English v.0.48:

Backsliding \Back"slid"ing\, n.
   The act of one who backslides; abandonment of faith or duty.
   [1913 Webster]

         Our backslidings are many.               --Jer. xiv. 7.
   [1913 Webster] backspace

The Collaborative International Dictionary of English v.0.48:

Backslide \Back"slide"\ (b[a^]k"sl[imac]d"; 277), v. i. [imp.
   Backslid; p. p. Backslidden, Backslid; p. pr. & vb. n.
   Backsliding.] [Back, adv. + slide.]
   To slide back; to fall away; esp. to abandon gradually the
   faith and practice of a religion that has been professed.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Backsliding \Back"slid"ing\, a.
   Slipping back; falling back into sin or error; sinning.
   [1913 Webster]

         Turn, O backsliding children, saith the Lord. --Jer.
                                                  iii. 14.
   [1913 Webster]

WordNet (r) 3.0 (2006):

backsliding
    n 1: a failure to maintain a higher state [syn: backsliding,
         lapse, lapsing, relapse, relapsing, reversion,
         reverting]

Moby Thesaurus II by Grady Ward, 1.0:

139 Moby Thesaurus words for "backsliding":
   Adamic, about-face, amorality, apostasy, apostate, atheism,
   atheistic, backing, backset, backslide, backward motion,
   backward step, betrayal, blasphemous, bolt, breakaway, carnal,
   carnality, criminality, defection, delinquency, desertion,
   disenchantment, disloyalty, erring, evil, evil nature,
   faithlessness, fall, fall from grace, fallen, fallen from grace,
   fleshly, flip-flop, frail, going over, immorality, impiety,
   impious, impiousness, impure, impurity, infirm, irreligion,
   irreligious, irreverence, irreverent, lapse, lapse from grace,
   lapsed, lapsing, moral delinquency, of easy virtue, peccability,
   peccable, postlapsarian, prodigal, prodigality, profanatory,
   profane, ratting, reaction, recession, recidivation, recidivism,
   recidivist, recidivistic, recidivous, reclamation, reconversion,
   recreancy, recreant, recrudescent, reentry, refluence, reflux,
   regress, regression, regressive, rehabilitation, reinstatement,
   relapse, relapsing, renegade, restitution, restoration,
   retroaction, retrocession, retroflexion, retrogradation,
   retrogression, retroversion, retrusion, return, returning,
   reversal, reverse, reversion, reverting, revulsion, rollback,
   sacrilegious, secession, setback, slipping back, sternway,
   throwback, treason, turn, turnabout, turning traitor, unangelic,
   unangelicalness, unchaste, unchastity, unclean, uncleanness,
   undutiful, undutifulness, ungodliness, ungodly, ungood, ungoodness,
   unmorality, unrighteous, unrighteousness, unsaintliness, unsaintly,
   unvirtuous, unvirtuousness, vice, viciousness, virtueless, wanton,
   wantonness, wayward, waywardness, weak, wrongdoing