Is method hiding a form of polymorphism?

using System;

public class A 
    {
    public void x() 	
  	{
        Console.WriteLine("A:x");
        }
    }

public class B : A 
    {
    public new void x() 
	{
        Console.WriteLine("B:x");
        }
    }

public class Program
    {
    public static void Main() 
	{
        A a = new B();
        a.x();
        }
    }