The Collaborative International Dictionary of English v.0.48:

Adopt \A*dopt"\, v. t. [imp. & p. p. Adopted; p. pr. & vb. n.
   Adopting.] [L. adoptare; ad + optare to choose, desire: cf.
   F. adopter. See Option.]
   1. To take by choice into relationship, as, child, heir,
      friend, citizen, etc.; esp. to take voluntarily (a child
      of other parents) to be in the place of, or as, one's own
      child.
      [1913 Webster]

   2. To take or receive as one's own what is not so naturally;
      to select and take or approve; as, to adopt the view or
      policy of another; these resolutions were adopted.
      [1913 Webster]

WordNet (r) 3.0 (2006):

adopt
    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 up and practice as one's own [syn: adopt, borrow,
       take over, take up]
    3: take on titles, offices, duties, responsibilities; "When will
       the new President assume office?" [syn: assume, adopt,
       take on, take over]
    4: take on a certain form, attribute, or aspect; "His voice took
       on a sad tone"; "The story took a new turn"; "he adopted an
       air of superiority"; "She assumed strange manners"; "The gods
       assume human or animal form in these fables" [syn: assume,
       acquire, adopt, take on, take]
    5: take into one's family; "They adopted two children from
       Nicaragua" [syn: adopt, take in]
    6: put into dramatic form; "adopt a book for a screenplay" [syn:
       dramatize, dramatise, adopt]
    7: 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:

65 Moby Thesaurus words for "adopt":
   Americanize, Anglicize, accept, acculturate, acculturize, admit,
   affect, affiliate, appropriate, approve, arrogate, assimilate,
   assume, carry, colonize, confer citizenship, conquer, copy,
   derive from, domesticate, embrace, encroach, enslave, espouse,
   go in for, go native, hog, imitate, indent, infringe, invade,
   jump a claim, make free with, make use of, mock, monopolize,
   naturalize, occupy, overrun, pass, pirate, plagiarize, play God,
   preempt, preoccupy, prepossess, pretend to, ratify, requisition,
   seize, simulate, sit on, squat on, steal, subjugate, take,
   take all of, take in, take it all, take on, take over,
   take possession of, take up, trespass, usurp