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]