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]