In computer science, polymorphism is a programming language feature that allows values of different data types to be handled in a uniform manner.

This may be ad hoc polymorphism (often synonymous with overloading) - or parametric polymorphism (as in ML or Haskell); but it's unclear what they actually do without some language semantics.

And to be more complete, OO-style polymorphism is usually referred to as "subtype polymorphism" and the parametric polymorphism dons talked about is like C++ or Java "generics"