The Collaborative International Dictionary of English v.0.48:

committed \committed\ adj.
   1. Bound or obligated, as under a pledge to a particular
      cause, action, or attitude. Opposite of uncommitted.

   Note: [Narrower terms: bound up, involved, wrapped up;
         dedicated, devoted; pledged, sworn]
         [WordNet 1.5]

   2. Associated in an exclusive sexual relationship; also
      called attached. Opposite of unattached.

   Note: [Narrower terms: affianced, bespoken, betrothed,
         engaged, pledged, promised(predicate); married]
         [Also See: loving.]

   Syn: attached.
        [WordNet 1.5]

   3. Consigned involuntarily to custody, as in a prison or
      mental institution.
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Pledge \Pledge\, v. t. [imp. & p. p. Pledged; p. pr. & vb. n.
   Pledging.] [Cf. OF. pleiger to give security. See Pledge,
   n.]
   1. To deposit, as a chattel, in pledge or pawn; to leave in
      possession of another as security; as, to pledge one's
      watch.
      [1913 Webster]

   2. To give or pass as a security; to guarantee; to engage; to
      plight; as, to pledge one's word and honor.
      [1913 Webster]

            We mutually pledge to each other our lives, our
            fortunes, and our sacred honor.       --The
                                                  Declaration of
                                                  Independence.
      [1913 Webster]

   3. To secure performance of, as by a pledge. [Obs.]
      [1913 Webster]

            To pledge my vow, I give my hand.     --Shak.
      [1913 Webster]

   4. To bind or engage by promise or declaration; to engage
      solemnly; as, to pledge one's self.
      [1913 Webster]

   5. To invite another to drink, by drinking of the cup first,
      and then handing it to him, as a pledge of good will;
      hence, to drink the health of; to toast.
      [1913 Webster]

            Pledge me, my friend, and drink till thou be'st
            wise.                                 --Cowley.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pledged
    adj 1: bound by or as if by an oath; "according to an early
           tradition became his sworn brother"; "sworn enemies"
           [syn: pledged, sworn]

Moby Thesaurus II by Grady Ward, 1.0:

66 Moby Thesaurus words for "pledged":
   affianced, affirmed, alleged, announced, answerable for,
   as earnest, asserted, asseverated, assured, at stake, attested,
   averred, avouched, avowed, beholden, beholden to, betrothed, bound,
   bounden, bounden to, certified, chargeable, committed, compromised,
   contracted, declared, deposed, deposited, duty-bound, engaged,
   enunciated, guaranteed, in duty bound, in hock, in pawn,
   indebted to, intended, liable, manifestoed, obligate, obligated,
   obliged, obliged to, on deposit, pawned, plighted, posted,
   predicated, professed, promised, pronounced, put up, responsible,
   saddled, staked, stated, sworn, sworn to, tied, under obligation,
   underwritten, up the spout, vouched, vouched for, vowed,
   warranted