The Collaborative International Dictionary of English v.0.48:

Chasten \Chas"ten\ (ch[=a]"s'n), v. t. [imp. & p. p. Chastened
   (-s'nd); p. pr. & vb. n. Chastening.] [OE. chastien, OF.
   Chastier, F. Ch?tier, fr. L. castigare to punish, chastise;
   castus pure + agere to lead, drive. See Chaste, Act, and
   cf. Castigate, Chastise.]
   1. To correct by punishment; to inflict pain upon the purpose
      of reclaiming; to discipline; as, to chasten a son with a
      rod.
      [1913 Webster]

            For whom the Lord loveth he chasteneth. --Heb. xii.
                                                  6.
      [1913 Webster]

   2. To purify from errors or faults; to refine.
      [1913 Webster]

            They [classics] chasten and enlarge the mind, and
            excite to noble actions.              --Layard.

   Syn: To chastise; punish; correct; discipline; castigate;
        afflict; subdue; purify.

   Usage: To Chasten, Punish, Chastise. To chasten is to
          subject to affliction or trouble, in order to produce
          a general change for the better in life or character.
          To punish is to inflict penalty for violation of law,
          disobedience to authority, or intentional wrongdoing.
          To chastise is to punish a particular offense, as with
          stripes, especially with the hope that suffering or
          disgrace may prevent a repetition of faults.
          [1913 Webster]

WordNet (r) 3.0 (2006):

chasten
    v 1: censure severely; "She chastised him for his insensitive
         remarks" [syn: chastise, castigate, objurgate,
         chasten, correct]
    2: restrain [syn: chasten, moderate, temper]
    3: correct by punishment or discipline [syn: tame, chasten,
       subdue]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "chasten":
   abate, allay, alleviate, assuage, attemper, bank the fire, blunt,
   bring to account, bring to book, call to account, castigate,
   chastise, constrain, control, correct, curb, damp, dampen,
   de-emphasize, deaden, deal with, diminish, discipline, downplay,
   dull, extenuate, inflict upon, keep within bounds, lay, lenify,
   lessen, lighten, masthead, mitigate, moderate, modulate, obtund,
   palliate, penalize, pillory, play down, punish, purify, reduce,
   reduce the temperature, repress, restrain, settle with, simplify,
   slacken, slow down, smother, sober, sober down, soften,
   square accounts, stifle, subdue, suppress, take to task, tame,
   temper, tone down, tune down, underplay, visit upon, weaken