Play that rolls the development of the game forward.
Since the stones don't move, one's understanding of what this might mean is a matter of experience. Many of the basic strategy concepts contribute: for example influence, exchange, running fights, miai.
Dynamic is a term often used in A Dictionary of Modern Fuseki -- The Korean Style to describe a desireable outcome as shown in the example immediately below.
Answering with the cut at is not good. Black's second approach at becomes an excellent move. The sequence to is a dynamic opening for Black. -- A Dictionary of Modern Fuseki -- The Korean Style page 85
Bill: I don't know about , but is decidedly undynamic. Surely Wa is better.