Link Details

If I understand what this says, "dynamic language" means the language has dynamic dispatch.

That's right.

Oops, "dynamic dispatch" can also refer to the capability for an object to be stored in a variable typed as one of the object's superclasses or interfaces, yet still dispatch methods called on the variable to the object's actual class (which inherits or implements the variable type). I should have remembered that distinction from C++ (virtual vs. non-virtual methods)....

I'll amend it to say that a "dynamic language" has "configurable message-passing", and hope that might make sense....

http://en.wikipedia.org/wiki/Dynamic_programming_language

And yet that definition doesn't include "meta-object protocol", which is what the article uses as a distinguishing characteristic.

I don't provide an over-arching definition for a dynamic programming language. I do say Groovy, Ruby and Python have a MOP. That does not mean a MOP is distinctive for all dynamic languages. Typical, maybe.