The Collaborative International Dictionary of English v.0.48:

Espousal \Es*pous"al\, n. [OF. espousailles, pl., F.
   ['e]pousailles, L. sponsalia, fr. sponsalis belonging to
   betrothal or espousal. See Espouse, and cf. Sponsal,
   Spousal.]
   1. The act of espousing or betrothing; especially, in the
      plural, betrothal; plighting of the troths; a contract of
      marriage; sometimes, the marriage ceremony.
      [1913 Webster]

   2. The uniting or allying one's self with anything;
      maintenance; adoption; as, the espousal of a quarrel.
      [1913 Webster]

            The open espousal of his cause.       --Lord Orford.
      [1913 Webster]

WordNet (r) 3.0 (2006):

espousal
    n 1: archaic terms for a wedding or wedding feast [syn:
         bridal, espousal]
    2: the act of becoming betrothed or engaged [syn: betrothal,
       espousal]
    3: the act of accepting with approval; favorable reception; "its
       adoption by society"; "the proposal found wide acceptance"
       [syn: adoption, acceptance, acceptation, espousal]

Moby Thesaurus II by Grady Ward, 1.0:

55 Moby Thesaurus words for "espousal":
   Gretna Green wedding, acceptance, adoption, advocacy, affiance,
   affiliation, aid, approval, banns, banns of matrimony, betrothal,
   betrothing, betrothment, bridal, bridal suite, bridechamber,
   chuppah, church wedding, civil ceremony, civil wedding, elopement,
   embracement, embracing, engagement, epithalamium, espousals,
   espousement, forced marriage, handfasting, honeymoon, hymen,
   hymeneal, hymeneal rites, marriage, marriage contract, mating,
   nuptial apartment, nuptial mass, nuptial song, nuptials,
   plighted faith, plighted troth, promotion, prothalamium,
   saffron veil, shotgun wedding, spousal, spousals, support, troth,
   union, wedding, wedding canopy, wedding song, wedding veil