The Collaborative International Dictionary of English v.0.48:

Conquer \Con"quer\ (k[o^][ng]"k[~e]r), v. t. [imp. & p. p.
   Conquered; p. pr. & vb. n. Conquering.] [OF. conquerre,
   F. conqu['e]rir, fr. L. conquirere, -quisitum, to seek or
   search for, to bring together, LL., to conquer; con- +
   quaerere to seek. See Quest.]
   1. To gain or acquire by force; to take possession of by
      violent means; to gain dominion over; to subdue by
      physical means; to reduce; to overcome by force of arms;
      to cause to yield; to vanquish. "If thou conquer Rome."
      --Shak.
      [1913 Webster]

            If we be conquer'd, let men conquer us. --Shak.
      [1913 Webster]

            We conquered France, but felt our captive's charms.
                                                  --Pope.
      [1913 Webster]

   2. To subdue or overcome by mental or moral power; to
      surmount; as, to conquer difficulties, temptation, etc.
      [1913 Webster]

            By winning words to conquer hearts,
            And make persuasion do the work of fear. --Milton.
      [1913 Webster]

   3. To gain or obtain, overcoming obstacles in the way; to
      win; as, to conquer freedom; to conquer a peace.

   Syn: To subdue; vanquish; overcome; overpower; overthrow;
        defeat; rout; discomfit; subjugate; reduce; humble;
        crush; surmount; subject; master.

   Usage: To Conquer, Vanquish, Subdue, Subjugate,
          Overcome. These words agree in the general idea
          expressed by overcome, -- that of bringing under one's
          power by the exertion of force. Conquer is wider and
          more general than vanquish, denoting usually a
          succession of conflicts. Vanquish is more individual,
          and refers usually to a single conflict. Thus,
          Alexander conquered Asia in a succession of battles,
          and vanquished Darius in one decisive engagement.
          Subdue implies a more gradual and continual pressure,
          but a surer and more final subjection. We speak of a
          nation as subdued when its spirit is at last broken,
          so that no further resistance is offered. Subjugate is
          to bring completely under the yoke of bondage. The
          ancient Gauls were never finally subdued by the Romans
          until they were completely subjugated. These words,
          when used figuratively, have correspondent meanings.
          We conquer our prejudices or aversions by a succesion
          of conflicts; but we sometimes vanquish our reluctance
          to duty by one decided effort: we endeavor to subdue
          our evil propensities by watchful and persevering
          exertions. Subjugate is more commonly taken in its
          primary meaning, and when used figuratively has
          generally a bad sense; as, his reason was completely
          subjugated to the sway of his passions.
          [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Conquer \Con"quer\ (k[o^][ng]"k[~e]r), v. i.
   To gain the victory; to overcome; to prevail.
   [1913 Webster]

         He went forth conquering and to conquer. --Rev. vi. 2.
   [1913 Webster]

         The champions resolved to conquer or to die. --Waller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

conquer
    v 1: to put down by force or authority; "suppress a nascent
         uprising"; "stamp down on littering"; "conquer one's
         desires" [syn: suppress, stamp down, inhibit,
         subdue, conquer, curb]
    2: take possession of by force, as after an invasion; "the
       invaders seized the land and property of the inhabitants";
       "The army seized the town"; "The militia captured the castle"
       [syn: appropriate, capture, seize, conquer]
    3: overcome by conquest; "conquer your fears"; "conquer a
       country"

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "conquer":
   acquire, adopt, annex, appropriate, arrogate, assume, baffle, balk,
   bear down, beat, beat down, bend, best, break, break down,
   bring low, bring to terms, capture, circumvent, colonize, control,
   crush, defeat, down, enslave, fell, flatten, foil, frustrate, gain,
   hog, humble, humiliate, hurdle, indent, jump a claim, lick,
   make free with, make use of, master, monopolize, obtain, occupy,
   outwit, overcome, overmaster, overpower, override, overrun,
   overwhelm, preempt, preoccupy, prepossess, prevail, prevail over,
   prostrate, put down, quell, reduce, requisition, ride down, seize,
   sit on, smash, squat on, subdue, subject, subjugate, suppress,
   surmount, take all of, take it all, take over, take possession of,
   take up, throw, thwart, trample down, trample underfoot,
   tread underfoot, triumph, triumph over, tyrannize, unman, usurp,
   vanquish, win, worst