The Collaborative International Dictionary of English v.0.48:

mapping \mapping\ n. (Math.)
   A function such that for every element of one set there is a
   unique element of another set.

   Syn: map, correspondence.
        [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Map \Map\, v. t. [imp. & p. p. Mapped; p. pr. & vb. n.
   Mapping.]
   To represent by a map; -- often with out; as, to survey and
   map, or map out, a county. Hence, figuratively: To represent
   or indicate systematically and clearly; to sketch; to plan;
   as, to map, or map out, a journey; to map out business.
   [1913 Webster]

         I am near to the place where they should meet, if
         Pisanio have mapped it truly.            --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

mapping
    n 1: (mathematics) a mathematical relation such that each
         element of a given set (the domain of the function) is
         associated with an element of another set (the range of the
         function) [syn: function, mathematical function,
         single-valued function, map, mapping]
    2: (genetics) the process of locating genes on a chromosome
       [syn: mapping, chromosome mapping]

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

function
mapping

   1.  (Or "map", "mapping") If D and C are sets
   (the domain and codomain) then a function f from D to C,
   normally written "f : D -> C" is a subset of D x C such that:

   1. For each d in D there exists some c in C such that (d,c) is
   an element of f.  I.e. the function is defined for every
   element of D.

   2. For each d in D, c1 and c2 in C, if both (d,c1) and (d,c2)
   are elements of f then c1 = c2.  I.e. the function is uniquely
   defined for every element of D.

   See also image, inverse, partial function.

   2.  Computing usage derives from the mathematical
   term but is much less strict.  In programming (except in
   functional programming), a function may return different
   values each time it is called with the same argument values
   and may have side effects.

   A procedure is a function which returns no value but has
   only side-effects.  The C language, for example, has no
   procedures, only functions.  ANSI C even defines a type,
   void, for the result of a function that has no result.

   (1996-09-01)