Source : Webster's Revised Unabridged Dictionary (1913)

Back \Back\, v. i. [imp. & p. p. {Backed}; p. pr. & vb. n.
   {Backing}.]
   1. To get upon the back of; to mount.

            I will back him [a horse] straight.   --Shak.

   2. To place or seat upon the back. [R.]

            Great Jupiter, upon his eagle backed, Appeared to
            me.                                   --Shak.

   3. To drive or force backward; to cause to retreat or recede;
      as, to back oxen.

   4. To make a back for; to furnish with a back; as, to back
      books.

   5. To adjoin behind; to be at the back of.

            A garden . . . with a vineyard backed. --Shak.

            The chalk cliffs which back the beach. --Huxley.

   6. To write upon the back of; as, to back a letter; to
      indorse; as, to back a note or legal document.

   7. To support; to maintain; to second or strengthen by aid or
      influence; as, to back a friend. ``Parliament would be
      backed by the people.'' --Macaulay.

            Have still found it necessary to back and fortify
            their laws with rewards and punishments. --South.

            The mate backed the captain manfully. --Blackw. Mag.

   8. To bet on the success of; -- as, to back a race horse.

   {To back an anchor} (Naut.), to lay down a small anchor ahead
      of a large one, the cable of the small one being fastened
      to the crown of the large one.

   {To back the field}, in horse racing, to bet against a
      particular horse or horses, that some one of all the other
      horses, collectively designated ``the field'', will win.
      

   {To back the oars}, to row backward with the oars.

   {To back a rope}, to put on a preventer.

   {To back the sails}, to arrange them so as to cause the ship
      to move astern.

   {To back up}, to support; to sustain; as, to back up one's
      friends.

   {To back a warrant} (Law), is for a justice of the peace, in
      the county where the warrant is to be executed, to sign or
      indorse a warrant, issued in another county, to apprehend
      an offender.

   {To back water} (Naut.), to reverse the action of the oars,
      paddles, or propeller, so as to force the boat or ship
      backward.

Backed \Backed\, a.
   Having a back; fitted with a back; as, a backed electrotype
   or stereotype plate. Used in composition; as, broad-backed;
   hump-backed.

Source : WordNet®

backed
     adj 1: having a back or backing, usually of a specified type [ant:
            {backless}]
     2: having backing; "a claim backed up by strong evidence" [syn:
         {backed up}]
     3: used of film that is coated on the side opposite the
        emulsion with a substance to absorb light