Source : Webster's Revised Unabridged Dictionary (1913)

Polymorphism \Pol`y*mor"phism\, n.
   1. (Crystallog.) Same as {Pleomorphism}.

   2. (Biol.)
      (a) The capability of assuming different forms; the
          capability of widely varying in form.
      (b) Existence in many forms; the coexistence, in the same
          locality, of two or more distinct forms independent of
          sex, not connected by intermediate gradations, but
          produced from common parents.

Source : WordNet®

polymorphism
     n 1: (chemistry) the existence of different kinds of crystal of
          the same chemical compound [syn: {pleomorphism}]
     2: (biology) the existence of two or more forms of individuals
        within the same animal species (independent of sex
        differences)

Source : Free On-Line Dictionary of Computing

polymorphism
     
         A concept first identified by
        {Christopher Strachey} (1967) and developed by Hindley and
        Milner, allowing {types} such as list of anything.  E.g. in
        {Haskell}:
     
        	length :: [a] -> Int
     
        is a function which operates on a list of objects of any type,
        a (a is a {type variable}).  This is known as parametric
        polymorphism.  Polymorphic typing allows strong type checking
        as well as generic functions.  {ML} in 1976 was the first
        language with polymorphic typing.
     
        Ad-hoc polymorphism (better described as {overloading}) is the
        ability to use the same syntax for objects of different types,
        e.g. "+" for addition of reals and integers or "-" for unary
        negation or diadic subtraction.  Parametric polymorphism
        allows the same object code for a function to handle arguments
        of many types but overloading only reuses syntax and requires
        different code to handle different types.
     
        See also {generic type variable}.
     
        In {object-oriented programming}, the term is used to describe
        a {variable} that may refer to objects whose {class} is not
        known at {compile time} and which respond at {run time}
        according to the actual class of the object to which they
        refer.
     
        (2002-08-08)