I guess, you already checked Wikipedia article on polymorphism.
In computer science, polymorphism is a programming language feature
that allows values of different data types to be handled using a
uniform interface.
According to that definition, no, C doesn't natively support polymorphism. For instance, there is no general function for acquiring absolute value of a number (abs and fabs are for integers and doubles respectively).
If you're also familiar with C++, take a look at OOP inheritance and templates - those are mechanisms for polymorphism there.
