The Collaborative International Dictionary of English v.0.48:

Polymorphic \Pol`y*mor"phic\, a.
   Polymorphous.
   [1913 Webster]

WordNet (r) 3.0 (2006):

polymorphic
    adj 1: relating to the crystallization of a compound in two or
           more different forms; "polymorphous crystallization"
           [syn: polymorphous, polymorphic]
    2: relating to the occurrence of more than one kind of
       individual (independent of sexual differences) in an
       interbreeding population; "a polymorphic species" [syn:
       polymorphic, polymorphous]
    3: having or occurring in several distinct forms; "man is both
       polymorphic and polytypic"; "a polymorphous god" [syn:
       polymorphic, polymorphous]

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

polymorphism
polymorphic

    The ability to leave parts of a type in a
   typed language unspecified.  The term has three distinct uses:

   * Parametric polymorphism refers to the use of type variables in
   a strongly typed language.

   * Overloading, sometimes called ad-hoc polymorphism, means
   using the same syntax for different types.

   * object-oriented polymorphism allows a variable to refer
   to objects whose class is not known at compile time.

   (2014-01-05)