The Collaborative International Dictionary of English v.0.48:

Espouse \Es*pouse"\, v. t. [imp. & p. p. Espoused; p. pr. &
   vb. n. Espousing.] [OF. espouser, esposer, F. ['e]pouser,
   L. sponsare to betroth, espouse, fr. sponsus betrothed, p. p.
   of spondere to promise solemnly or sacredly. Cf. Spouse.]
   1. To betroth; to promise in marriage; to give as spouse.
      [1913 Webster]

            A virgin espoused to a man whose name was Joseph.
                                                  --Luke i. 27.
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   2. To take as spouse; to take to wife; to marry.
      [1913 Webster]

            Lavinia will I make my empress, . . .
            And in the sacred Pantheon her espouse. --Shak.
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   3. To take to one's self with a view to maintain; to make
      one's own; to take up the cause of; to adopt; to embrace.
      "He espoused that quarrel." --Bacon.
      [1913 Webster]

            Promised faithfully to espouse his cause as soon as
            he got out of the war.                --Bp. Burnet.
      [1913 Webster]

WordNet (r) 3.0 (2006):

espouse
    v 1: choose and follow; as of theories, ideas, policies,
         strategies or plans; "She followed the feminist movement";
         "The candidate espouses Republican ideals" [syn: adopt,
         follow, espouse]
    2: take in marriage [syn: marry, get married, wed,
       conjoin, hook up with, get hitched with, espouse]
    3: take up the cause, ideology, practice, method, of someone and
       use it as one's own; "She embraced Catholicism"; "They
       adopted the Jewish faith" [syn: espouse, embrace,
       adopt, sweep up]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "espouse":
   accept, adopt, advocate, affiliate, allege in support, answer,
   approve, argue for, assert, back, be made one, be spliced,
   become one, campaign for, carry, catch, champion, contend for,
   contract matrimony, counter, couple, crusade for, defend, embrace,
   get hitched, go in for, intermarry, interwed, maintain,
   make a plea, marry, mate, miscegenate, pair off, pass, plead for,
   ratify, rebut, refute, remarry, reply, respond, rewed, riposte,
   say in defense, speak for, speak up for, stand up for,
   stick up for, support, sustain, take on, take to wife, take up,
   uphold, urge reasons for, wed, wive



Easton's 1897 Bible Dictionary:

Espouse
   (2 Sam. 3:14), to betroth. The espousal was a ceremony of
   betrothing, a formal agreement between the parties then coming
   under obligation for the purpose of marriage. Espousals are in
   the East frequently contracted years before the marriage is
   celebrated. It is referred to as figuratively illustrating the
   relations between God and his people (Jer. 2:2; Matt. 1:18; 2
   Cor. 11:2). (See BETROTH.)