The Collaborative International Dictionary of English v.0.48:

Back \Back\ (b[a^]k), v. t. [imp. & p. p. Backed (b[a^]kt); p.
   pr. & vb. n. Backing.]
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   1. To get upon the back of; to mount.
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            I will back him [a horse] straight.   --Shak.
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   2. To place or seat upon the back. [R.]
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            Great Jupiter, upon his eagle backed,
            Appeared to me.                       --Shak.
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   3. To drive or force backward; to cause to retreat or recede;
      as, to back oxen.
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   4. To make a back for; to furnish with a back; as, to back
      books.
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   5. To adjoin behind; to be at the back of.
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            A garden . . . with a vineyard backed. --Shak.
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            The chalk cliffs which back the beach. --Huxley.
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   6. To write upon the back of; as, to back a letter; to
      indorse; as, to back a note or legal document.
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   7. To support; to maintain; to second or strengthen by aid or
      influence; as, to back a friend. "The Parliament would be
      backed by the people." --Macaulay.
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            Have still found it necessary to back and fortify
            their laws with rewards and punishments. --South.
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            The mate backed the captain manfully. --Blackw. Mag.
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   8. To bet on the success of; -- as, to back a race horse.
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   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.
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The Collaborative International Dictionary of English v.0.48:

Backed \Backed\ (b[a^]kt), a.
   Having a back; fitted with a back; as, a backed electrotype
   or stereotype plate. Used in composition; as, broad-backed;
   hump-backed.
   [1913 Webster]

WordNet (r) 3.0 (2006):

backed
    adj 1: having a back or backing, usually of a specified type
           [ant: backless]
    2: used of film that is coated on the side opposite the emulsion
       with a substance to absorb light

Moby Thesaurus II by Grady Ward, 1.0:

44 Moby Thesaurus words for "backed":
   accepted, acclaimed, admired, admitted, advocated, applauded,
   approved, calcified, callous, calloused, case-hardened, cried up,
   crusted, crusty, crystallized, favored, favorite, fossilized,
   granulated, hardened, highly touted, hornified, in good odor,
   incrusted, indurate, indurated, lapidified, ossified, petrified,
   popular, received, recommended, reinforced, rigidified, sclerotic,
   set, solidified, steeled, stiffened, strengthened, supported,
   toughened, vitrified, well-thought-of