The Collaborative International Dictionary of English v.0.48:

Subjugate \Sub"ju*gate\, v. t. [imp. & p. p. Subjugated; p.
   pr. & vb. n. Subjugating.] [L. subjugatus, p. p. of
   subjugare to subjugate; sub under + jugum a yoke. See
   Yoke.]
   To subdue, and bring under the yoke of power or dominion; to
   conquer by force, and compel to submit to the government or
   absolute control of another; to vanquish.
   [1913 Webster]

         He subjugated a king, and called him his "vassal."
                                                  --Baker.
   [1913 Webster]

   Syn: To conquer; subdue; overcome. See Conquer.
        [1913 Webster]

WordNet (r) 3.0 (2006):

subjugate
    v 1: put down by force or intimidation; "The government quashes
         any attempt of an uprising"; "China keeps down her
         dissidents very efficiently"; "The rich landowners
         subjugated the peasants working the land" [syn: repress,
         quash, keep down, subdue, subjugate, reduce]
    2: make subservient; force to submit or subdue [syn:
       subjugate, subject]

Moby Thesaurus II by Grady Ward, 1.0:

107 Moby Thesaurus words for "subjugate":
   adopt, appropriate, arrogate, assume, bear down, beat down, bend,
   break, browbeat, bulldoze, bully, castrate, clamp down on, compel,
   conquer, cow, crush, daunt, defeat, deprive of freedom, despotize,
   disenfranchise, disfranchise, dominate, domineer, domineer over,
   enslave, enthrall, fell, flatten, force, grind, grind down,
   henpeck, hog, hold captive, hold down, hold in bondage,
   hold in captivity, hold in leash, hold in subjection, humble,
   humiliate, indent, intimidate, jump a claim, keep down, keep under,
   lead captive, lord it over, make dependent, make free with,
   make use of, master, monopolize, occupy, oppress, overawe,
   overbear, overcome, overmaster, overpower, override, overrun,
   peonize, preempt, preoccupy, prepossess, press heavy on, prostrate,
   put down, quell, reduce, repress, requisition, ride down,
   ride over, ride roughshod over, sit on, smash, squat on, subdue,
   subject, subordinate, suppress, take all of, take captive,
   take it all, take over, take possession of, take up, terrorize,
   trample down, trample underfoot, trample upon, tread down,
   tread underfoot, tread upon, tyrannize, tyrannize over, unman,
   usurp, vanquish, vassalize, walk all over, walk over,
   weigh heavy on