Source : Webster's Revised Unabridged Dictionary (1913)

Dummy \Dum"my\, a. [See {Dumb}.]
   1. Silent; mute; noiseless; as a dummy engine.

   2. Fictitious or sham; feigned; as, a dummy watch.

   {Dummy car}. See under {Car}.

Dummy \Dum"my\, n.; pl. {Dummies}.
   1. One who is dumb. --H. Smith.

   2. A sham package in a shop, or one which does not contain
      what its exterior indicates.

   3. An imitation or copy of something, to be used as a
      substitute; a model; a lay figure; as, a figure on which
      clothing is exhibited in shop windows; a blank paper copy
      used to show the size of the future book, etc.

   4. (Drama) One who plays a merely nominal part in any action;
      a sham character.

   5. A thick-witted person; a dolt. [Colloq.]

   6. (Railroad) A locomotive with condensing engines, and,
      hence, without the noise of escaping steam; also, a dummy
      car.

   7. (Card Playing) The fourth or exposed hand when three
      persons play at a four-handed game of cards.

   8. A floating barge connected with a pier. --Knight.

   {To play dummy}, to play the exposed or dummy hand in cards.
      The partner of the dummy plays it.

Source : WordNet®

dummy
     adj : having the appearance of being real but lacking capacity to
           function; "a dummy corporation"
     n 1: a person who does not talk [syn: {silent person}]
     2: an ignorant or foolish person [syn: {dumbbell}, {dope}, {boob},
         {booby}, {pinhead}]
     3: a figure representing the human form
     4: a cartridge containing an explosive charge but no bullet
        [syn: {blank}, {blank shell}]
     [also: {dummied}]

dummy
     v : make a dummy of; "dummy up the books that are to be
         published" [syn: {dummy up}]
     [also: {dummied}]