The Collaborative International Dictionary of English v.0.48:

Enfranchise \En*fran"chise\, v. t. [imp. & p. p. Enfranchised;
   p. pr. & vb. n. Enfranchising.] [Pref. en- + franchise: cf.
   F. enfranchir.]
   1. To set free; to liberate from slavery, prison, or any
      binding power. --Bacon.
      [1913 Webster]

   2. To endow with a franchise; to incorporate into a body
      politic and thus to invest with civil and political
      privileges; to admit to the privileges of a freeman; to
      give the right to vote.
      [1913 Webster]

   3. To receive as denizens; to naturalize; as, to enfranchise
      foreign words. --I. Watts.
      [1913 Webster]

WordNet (r) 3.0 (2006):

enfranchise
    v 1: grant freedom to; as from slavery or servitude; "Slaves
         were enfranchised in the mid-19th century" [syn:
         affranchise, enfranchise]
    2: grant voting rights [ant: disenfranchise, disfranchise]

Moby Thesaurus II by Grady Ward, 1.0:

32 Moby Thesaurus words for "enfranchise":
   affranchise, authorize, certificate, certify, charter, deliver,
   disenthrall, emancipate, empower, enable, entitle, extricate,
   franchise, free, give official sanction, give power, legalize,
   legitimize, liberate, license, manumit, patent, privilege, ratify,
   release, rescue, sanction, set at large, set at liberty, set free,
   validate, warrant