The Collaborative International Dictionary of English v.0.48:

Variable \Va"ri*a*ble\, a. [L. variabilis: cf. F. variable.]
   1. Having the capacity of varying or changing; capable of
      alternation in any manner; changeable; as, variable winds
      or seasons; a variable quantity.
      [1913 Webster]

   2. Liable to vary; too susceptible of change; mutable;
      fickle; unsteady; inconstant; as, the affections of men
      are variable; passions are variable.
      [1913 Webster]

            Lest that thy love prove likewise variable. --Shak.
      [1913 Webster]

            His heart, I know, how variable and vain! --Milton.
      [1913 Webster]

   Variable exhaust (Steam Eng.), a blast pipe with an
      adjustable opening.

   Variable quantity (Math.), a variable.

   Variable-rate mortgage (Finance), a mortgage whose
      percentage interest rate varies depending on some agreed
      standard, such as the prime rate; -- used often in
      financing the purchase of a home. Such a mortgage usually
      has a lower initial interest rate than a fixed-rate
      mortgage, and this permits buyers of a home to finance
      the purchase a house of higher price than would be
      possible with a fixed-rate loan.

   Variable stars (Astron.), fixed stars which vary in their
      brightness, usually in more or less uniform periods.
      [1913 Webster]

   Syn: Changeable; mutable; fickle; wavering; unsteady;
        versatile; inconstant.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Variable \Va"ri*a*ble\, n.
   1. That which is variable; that which varies, or is subject
      to change.
      [1913 Webster]

   2. (Math.) A quantity which may increase or decrease; a
      quantity which admits of an infinite number of values in
      the same expression; a variable quantity; as, in the
      equation x^2 - y^2 = R^2, x and y are variables.
      [1913 Webster]

   3. (Naut.)
      (a) A shifting wind, or one that varies in force.
      (b) pl. Those parts of the sea where a steady wind is not
          expected, especially the parts between the trade-wind
          belts.
          [1913 Webster]

   Independent variable (Math.), that one of two or more
      variables, connected with each other in any way whatever,
      to which changes are supposed to be given at will. Thus,
      in the equation x^2 - y^2 = R^2, if arbitrary
      changes are supposed to be given to x, then x is the
      independent variable, and y is called a function of x.
      There may be two or more independent variables in an
      equation or problem. Cf. Dependent variable, under
      Dependent.
      [1913 Webster]

WordNet (r) 3.0 (2006):

variable
    adj 1: liable to or capable of change; "rainfall in the tropics
           is notoriously variable"; "variable winds"; "variable
           expenses" [ant: invariable]
    2: marked by diversity or difference; "the varying angles of
       roof slope"; "nature is infinitely variable" [syn: varying,
       variable]
    3: (used of a device) designed so that a property (as e.g.
       light) can be varied; "a variable capacitor"; "variable
       filters in front of the mercury xenon lights"
    n 1: something that is likely to vary; something that is subject
         to variation; "the weather is one variable to be
         considered"
    2: a quantity that can assume any of a set of values [syn:
       variable, variable quantity]
    3: a star that varies noticeably in brightness [syn: variable
       star, variable]
    4: a symbol (like x or y) that is used in mathematical or
       logical expressions to represent a variable quantity

Moby Thesaurus II by Grady Ward, 1.0:

181 Moby Thesaurus words for "variable":
   able to adapt, adaptable, adjustable, adrift, afloat, agnostic,
   alterable, alterative, alternating, ambiguous, amorphous, broken,
   capricious, careening, catchy, chancy, changeable, changeful,
   changing, checkered, choppy, desultory, deviable, deviating,
   deviative, deviatory, dicey, different, disconnected,
   discontinuous, disorderly, divaricate, divergent, diversified,
   diversiform, dizzy, doubting, eccentric, equivocal, erose, erratic,
   ever-changing, fast and loose, fickle, fitful, flexible,
   flickering, flighty, flitting, fluctuating, fluid, freakish, giddy,
   guttering, halting, herky-jerky, hesitant, hesitating, heteroclite,
   immethodical, impermanent, impetuous, impulsive, incalculable,
   inconsistent, inconstant, indecisive, indemonstrable, infirm,
   intermittent, intermitting, irregular, irresolute, irresponsible,
   jagged, jerky, kaleidoscopic, lurching, malleable, many-sided,
   mazy, mercurial, metamorphic, mobile, modifiable, moody, motley,
   movable, mutable, nonconformist, nonstandard, nonuniform, patchy,
   permutable, plastic, pluralistic, polysemous, protean, proteiform,
   ragged, rambling, resilient, restless, rough, roving, rubbery,
   scatterbrained, scrappy, shapeless, shifting, shifty, shuffling,
   skeptical, slippery, snatchy, spasmatic, spasmic, spasmodic,
   spastic, spineless, sporadic, spotty, staggering, supple,
   temperamental, ticklish, touch-and-go, transient, transitory,
   uncertain, unconfirmable, uncontrolled, unconvinced, undependable,
   undisciplined, undivinable, unequable, unequal, uneven, unfixed,
   unforeseeable, unmethodical, unmetrical, unorthodox, unpersuaded,
   unpredictable, unprovable, unregular, unreliable, unrestrained,
   unrhythmical, unsettled, unstable, unstable as water, unstaid,
   unsteadfast, unsteady, unsure, unsystematic, ununiform,
   unverifiable, vacillating, vagrant, variegated, variform, various,
   varying, veering, vicissitudinary, vicissitudinous, volatile,
   wandering, wanton, wavering, wavery, wavy, wayward, whimsical,
   wishy-washy, wobbling, wobbly



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

variable
var

    (Sometimes "var" /veir/ or /var/) A named memory
   location in which a program can store intermediate results and
   from which it can read it them.  Each programming language
   has different rules about how variables can be named, typed,
   and used.  Typically, a value is "assigned" to a variable in
   an assignment statement.  The value is obtained by
   evaluating an expression and then stored in the variable.  For
   example, the assignment

   	x = y + 1

   means "add one to y and store the result in x".  This may look
   like a mathematical equation but the mathematical equality is
   only true in the program until the value of x or y changes.
   Furthermore, statements like

   	x = x + 1

   are common.  This means "add one to x", which only makes sense
   as a state changing operation, not as a mathematical equality.

   The simplest form of variable corresponds to a single-word
   of memory or a CPU register and an assignment to a
   load or store machine code operation.

   A variable is usually defined to have a type, which never
   changes, and which defines the set of values the variable can
   hold.  A type may specify a single ("atomic") value or a
   collection ("aggregate") of values of the same or different
   types.  A common aggregate type is the array - a set of
   values, one of which can be selected by supplying a numerical
   index.

   Languages may be untyped, weakly typed, strongly typed,
   or some combination.  Object-oriented programming languages
   extend this to object types or classes.

   A variable's scope is the region of the program source
   within which it represents a certain thing.  Scoping rules are
   also highly language dependent but most serious languages
   support both local variables and global variables.
   Subroutine and function formal arguments are special
   variables which are set automatically by the language runtime
   on entry to the subroutine.

   In a functional programming language, a variable's value
   never changes and change of state is handled as recursion over
   lists of values.

   (2004-11-16)