The Collaborative International Dictionary of English v.0.48:

neuter \neu"ter\, v. t.
   To render incapable of sexual reproduction; to remove or
   alter the sexual organs so as to make infertile; to alter; to
   fix; to desex; -- in male animals, to castrate; in female
   animals, to spay.
   [PJC]

The Collaborative International Dictionary of English v.0.48:

Castrate \Cas"trate\, v. t. [imp. & p. p. Castrated; p. pr. &
   vb. n. Castrating.] [L. castrarus, p; p. of castrare to
   castrate, asin to Skr. [,c]astra knife.]
   1. To deprive of the testicles; to emasculate; to geld; to
      alter.
      [1913 Webster]

   2. To cut or take out; esp. to remove anything erroneous, or
      objectionable from, as the obscene parts of a writing; to
      expurgate.
      [1913 Webster]

            My . . . correspondent . . . has sent me the
            following letter, which I have castrated in some
            places.                               --Spectator.
      [1913 Webster]

WordNet (r) 3.0 (2006):

castrate
    n 1: a man who has been castrated and is incapable of
         reproduction; "eunuchs guarded the harem" [syn: eunuch,
         castrate]
    v 1: deprive of strength or vigor; "The Senate emasculated the
         law" [syn: emasculate, castrate]
    2: edit by omitting or modifying parts considered indelicate;
       "bowdlerize a novel" [syn: bowdlerize, bowdlerise,
       expurgate, castrate, shorten]
    3: remove the testicles of a male animal [syn: emasculate,
       castrate, demasculinize, demasculinise]
    4: remove the ovaries of; "Is your cat spayed?" [syn: alter,
       neuter, spay, castrate]

Moby Thesaurus II by Grady Ward, 1.0:

80 Moby Thesaurus words for "castrate":
   alter, beat down, bleed, break, browbeat, bulldoze, bully, change,
   clamp down on, coerce, compel, cow, cripple, daunt, demasculinize,
   desex, desexualize, despotize, devitalize, disable, domineer,
   domineer over, drain, effeminate, effeminatize, effeminize,
   emasculate, empty, enervate, enslave, etiolate, eunuchize, exhaust,
   fix, geld, grind, grind down, hamstring, henpeck, hobble,
   incapacitate, intimidate, keep down, keep under, lame,
   lord it over, maim, mutilate, neuter, oppress, overawe, overbear,
   overmaster, override, press heavy on, repress, ride over,
   ride roughshod over, sissify, soften, spay, sterilize, subjugate,
   suppress, terrorize, trample down, trample upon, tread down,
   tread upon, tyrannize, tyrannize over, unman, unnerve, unsex,
   unstring, walk all over, walk over, weigh heavy on, wing,
   womanize