Source : Webster's Revised Unabridged Dictionary (1913)

Pledge \Pledge\, n. [OF. plege, pleige, pledge, guaranty, LL.
   plegium, plivium; akin to OF. plevir to bail, guaranty,
   perhaps fr. L. praebere to proffer, offer (sc. fidem a trust,
   a promise of security), but cf. also E. play. [root]28. Cf.
   {Prebend}, {Replevin}.]
   1. (Law) The transfer of possession of personal property from
      a debtor to a creditor as security for a debt or
      engagement; also, the contract created between the debtor
      and creditor by a thing being so delivered or deposited,
      forming a species of bailment; also, that which is so
      delivered or deposited; something put in pawn.

   Note: Pledge is ordinarily confined to personal property; the
         title or ownership does not pass by it; possession is
         essential to it. In all these points it differs from a
         mortgage [see {Mortgage}]; and in the last, from the
         hypotheca of the Roman law. See {Hypotheca}. --Story.
         Kent.

   2. (Old Eng. Law) A person who undertook, or became
      responsible, for another; a bail; a surety; a hostage. ``I
      am Grumio's pledge.'' --Shak.

   3. A hypothecation without transfer of possession.

   4. Anything given or considered as a security for the
      performance of an act; a guarantee; as, mutual interest is
      the best pledge for the performance of treaties. ``That
      voice, their liveliest pledge of hope.'' --Milton.

   5. A promise or agreement by which one binds one's self to
      do, or to refrain from doing, something; especially, a
      solemn promise in writing to refrain from using
      intoxicating liquors or the like; as, to sign the pledge;
      the mayor had made no pledges.

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.

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

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

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

            To pledge my vow, I give my hand.     --Shak.

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

   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.

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

Source : WordNet®

pledge
     n 1: a deposit of personal property as security for a debt; "his
          saxophone was in pledge"
     2: someone accepted for membership but not yet fully admitted
        to the group
     3: a drink in honor of or to the health of a person or event
        [syn: {toast}]
     4: a binding commitment to do or give or refrain from
        something; "an assurance of help when needed"; "signed a
        pledge never to reveal the secret" [syn: {assurance}]

pledge
     v 1: promise solemnly and formally; "I pledge that will honor my
          wife" [syn: {plight}]
     2: pay (an amount of money) as a contribution to a charity or
        service, especially at regular intervals; "I pledged $10 a
        month to my favorite radio station" [syn: {subscribe}]
     3: propose a toast to; "Let us toast the birthday girl!";
        "Let's drink to the New Year" [syn: {toast}, {drink}, {salute},
         {wassail}]
     4: give as a guarantee; "I pledge my honor"
     5: bind or secure by a pledge; "I was pledged to silence"