The Collaborative International Dictionary of English v.0.48:

Castigate \Cas"ti*gate\, v. t. [imp. & p. p. Castigated; p.
   pr. & vb. n. Castigating.] [L. castigatus, p. p. of
   castigare to correct, punish; castus pure, chaste + agere to
   move, drive. See Caste, and cf. Chasten.]
   1. To punish by stripes; to chastise by blows; to chasten;
      also, to chastise verbally; to reprove; to criticise
      severely.
      [1913 Webster]

   2. To emend; to correct. [Obs.]
      [1913 Webster]

WordNet (r) 3.0 (2006):

castigate
    v 1: censure severely; "She chastised him for his insensitive
         remarks" [syn: chastise, castigate, objurgate,
         chasten, correct]
    2: inflict severe punishment on

Moby Thesaurus II by Grady Ward, 1.0:

53 Moby Thesaurus words for "castigate":
   assail, attack, baste, beat, belabor, berate, blister,
   bring to account, bring to book, call to account, carpet, chasten,
   chastise, chew out, correct, criticize, deal with, discipline,
   dress down, drub, excoriate, flay, fustigate, inflict upon,
   keelhaul, lash, masthead, penalize, pillory, pummel, punish, rail,
   rate, rebuke, reprimand, roast, scarify, scathe, scorch, scourge,
   settle with, skin alive, slash, square accounts, take to task,
   tell off, thrash, tick off, tongue-lash, trounce, upbraid,
   visit upon, wig