The Collaborative International Dictionary of English v.0.48:

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 tendon; the
      contraction produced by cold.
      [1913 Webster]

   2. (Math.) The process of shortening an operation.
      [1913 Webster]

   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.
      [1913 Webster]

   4. Something contracted or abbreviated, as a word or phrase;
      -- as, plenipo for plenipotentiary; crim. con. for
      criminal conversation, etc.
      [1913 Webster]

   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.
      [1913 Webster]

   6. A marriage contract. [Obs.] --Shak.
      [1913 Webster]

WordNet (r) 3.0 (2006):

contraction
    n 1: (physiology) a shortening or tensing of a part or organ
         (especially of a muscle or muscle fiber) [syn:
         contraction, 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, contraction]
    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: enlargement, expansion]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "contraction":
   Speedwriting, abatement, abbreviation, abridgment, alleviation,
   apocope, aposiopesis, attenuation, brachygraphy, clipping,
   coarctation, constriction, crasis, cutting, dampening, damping,
   decrease, decrement, decrescence, deduction, deflation,
   depreciation, depression, diminishment, diminution, dying,
   dying off, elision, ellipsis, extenuation, fade-out, languishment,
   lessening, letup, lowering, miniaturization, mitigation, narrowing,
   phonography, pruning, reduction, relaxation, sagging, scaling down,
   shortening, shorthand, simplicity, stenography, stricture,
   subtraction, syncope, syneresis, tachygraphy, taper, tapering,
   truncation, weakening



The Free On-line Dictionary of Computing (30 December 2018):

reduction
contraction

   (Or "contraction") The process of transforming an expression
   according to certain reduction rules.  The most important
   forms are beta reduction (application of a lambda
   abstraction to one or more argument expressions) and delta
   reduction (application of a mathematical function to the
   required number of arguments).

   An evaluation strategy (or reduction strategy), determines
   which part of an expression (which redex) to reduce first.
   There are many such strategies.

   See graph reduction, string reduction, normal order
   reduction, applicative order reduction, parallel
   reduction, alpha conversion, beta conversion, delta
   conversion, eta conversion.

   (1995-02-21)


Bouvier's Law Dictionary, Revised 6th Ed (1856):

CONTRACTION. An abbreviation; a mode of writing or printing by which some of
the letters of a word are omitted. See Abbreviations.