Scoring despite good opposing defense.
I think that this statement is the essence of what people mean when they say "dynamic scorer."
A player who can score points even if the opposing defense is focused on preventing him from doing that.
Typically, that means a player has a skillset that allows him to score without relying on one particular method of scoring. If the opponent takes away one thing he does well, he can do it a different way.
Alternatively, it could be a player who is just so dominant in one area that it is impossible to completely prevent him from scoring that way (e.g. Ray Allen and Kyle Korver finding ways to score from deep, or Shaq in the post).