Source : Webster's Revised Unabridged Dictionary (1913)

Shim \Shim\, n.
   1. A kind of shallow plow used in tillage to break the
      ground, and clear it of weeds.

   2. (Mach.) A thin piece of metal placed between two parts to
      make a fit.

Source : WordNet®

shim
     n : a thin wedge of material (wood or metal or stone) for
         driving into crevices
     [also: {shimming}, {shimmed}]

Source : Free On-Line Dictionary of Computing

shim
     
         A small piece of data inserted in order to
        achieve a desired {memory alignment} or other addressing
        property.  For example, the {PDP-11} {Unix} {linker}, in split
        I&D (instructions and data) mode, inserts a two-{byte} shim at
        location 0 in data space so that no data object will have an
        address of 0 (and be confused with the {C} null pointer).
     
        See also {loose bytes}.
     
        [{Jargon File}]
     
        (1994-12-21)