The Collaborative International Dictionary of English v.0.48:

Peccant \Pec"cant\, a. [L. peccans, -antis, p. pr. of peccare to
   sin: cf. F. peccant.]
   1. Sinning; guilty of transgression; criminal; as, peccant
      angels. --Milton.
      [1913 Webster]

   2. Morbid; corrupt; as, peccant humors. --Bacon.
      [1913 Webster]

   3. Wrong; defective; faulty. [R.] --Ayliffe.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Peccant \Pec"cant\, n.
   An offender. [Obs.] --Whitlock.
   [1913 Webster]

WordNet (r) 3.0 (2006):

peccant
    adj 1: liable to sin; "a frail and peccable mortal"- Sir Walter
           Scott [syn: peccable, peccant]

Moby Thesaurus II by Grady Ward, 1.0:

158 Moby Thesaurus words for "peccant":
   aberrant, abominable, abroad, adrift, all abroad, all off,
   all wrong, amiss, arraignable, arrant, askew, astray, at fault,
   atrocious, awry, bad, bad for, base, beside the mark, black,
   blamable, blameworthy, cankered, carious, censurable, contaminated,
   corrupt, criminal, culpable, damnable, dark, decayed, deceptive,
   decomposed, defective, delusive, deviant, deviational, deviative,
   diseased, disgraceful, distorted, errant, erring, erroneous, evil,
   execrable, fallacious, false, faultful, faulty, festering,
   flagitious, flagrant, flawed, foul, gangrened, gangrenous,
   gone bad, guilty, harmful, heinous, heretical, heterodox, ill,
   illogical, illusory, impeachable, implicated, improper, inaccurate,
   inauspicious, inculpated, indictable, inexpedient, infamous,
   infected, inferior, iniquitous, injurious, insalubrious,
   insanitary, invalid, involved, knavish, low, malevolent, monstrous,
   morbid, morbific, mortified, naughty, necrosed, necrotic,
   nefarious, noisome, not right, not true, noxious, off,
   off the track, out, pathogenic, pathological, perverse, perverted,
   pestiferous, poisoned, polluted, putrefied, putrescent, putrid,
   rank, reprehensible, reproachable, reprobate, reprovable, rotten,
   rotting, scandalous, self-contradictory, septic, shameful, sinful,
   sinister, sphacelated, spoiled, straying, suppurating, suppurative,
   tainted, to blame, ulcerated, ulcerous, unfactual, unfavorable,
   unforgivable, unhealthful, unhealthy, unhygienic, unkind,
   unorthodox, unpardonable, unpleasant, unproved, unsanitary,
   unskillful, unspeakable, untoward, untrue, unwholesome, unworthy,
   vicious, vile, villainous, wicked, wide, wrong