Note that some people use the term "polymorphism" for a much more general concept - sometimes method overloading is also called "compile time polymorphism", for example. In that sense, dynamic method lookup is a specific form of (runtime) polymorphism.
The soul is dyed the color of its thoughts. Think only on those things that are in line with your principles and can bear the light of day. The content of your character is your choice. Day by day, what you do is who you become. Your integrity is your destiny - it is the light that guides your way. - Heraclitus