Source : Webster's Revised Unabridged Dictionary (1913)

Decomposition \De*com`po*si"tion\, n. [Pref. de- (in sense 3
   intensive) + composition: cf. F. d['e]composition. Cf.
   {Decomposition}.]
   1. The act or process of resolving the constituent parts of a
      compound body or substance into its elementary parts;
      separation into constituent part; analysis; the decay or
      dissolution consequent on the removal or alteration of
      some of the ingredients of a compound; disintegration; as,
      the decomposition of wood, rocks, etc.

   2. The state of being reduced into original elements.

   3. Repeated composition; a combination of compounds. [Obs.]

   {Decomposition of forces}. Same as {Resolution of forces},
      under {Resolution}.

   {Decomposition of light}, the division of light into the
      prismatic colors.

Source : WordNet®

decomposition
     n 1: the analysis of a vector field [syn: {vector decomposition}]
     2: in a decomposed state [syn: {disintegration}]
     3: (chemistry) separation of a substance into two or more
        substances that may differ from each other and from the
        original substance [syn: {decomposition reaction}]
     4: the organic phenomenon of rotting [syn: {decay}]
     5: (biology) decaying caused by bacterial or fungal action
        [syn: {rot}, {rotting}, {putrefaction}]