Source : Webster's Revised Unabridged Dictionary (1913)

Contraction \Con*trac"tion\, n. [L. contractio: cf. F.
   contraction.]
   1. The act or process of contracting, shortening, or
      shrinking; the state of being contracted; as, contraction
      of the heart, of the pupil of the eye, or of a tendion;
      the contraction produced by cold.

   2. (Math.) The process of shortening an operation.

   3. The act of incurring or becoming subject to, as
      liabilities, obligation, debts, etc.; the process of
      becoming subject to; as, the contraction of a disease.

   4. Something contracted or abbreviated, as a word or phrase;
      -- as, plenipo for plenipotentiary; crim. con. for
      criminal conversation, etc.

   5. (Gram.) The shortening of a word, or of two words, by the
      omission of a letter or letters, or by reducing two or
      more vowels or syllables to one; as, ne'er for never;
      can't for can not; don't for do not; it's for it is.

   6. A marriage contract. [Obs.] --Shak.

Source : WordNet®

contraction
     n 1: (physiology) a shortening or tensing of a part or organ
          (especially of a muscle or muscle fiber) [syn: {muscular
          contraction}, {muscle contraction}]
     2: the process or result of becoming smaller or pressed
        together; "the contraction of a gas on cooling" [syn: {compression},
         {condensation}]
     3: a word formed from two or more words by omitting or
        combining some sounds; "`won't' is a contraction of `will
        not'"; "`o'clock' is a contraction of `of the clock'"
     4: the act of decreasing (something) in size or volume or
        quantity or scope [ant: {expansion}]

Source : Free On-Line Dictionary of Computing

contraction
     
        {reduction}