ISO as in ISOLATION or "insolation-heavy offense" usually associated with Carmelo.
Basically, when Carmelo gets the ball, he brings the offense to a halt and he takes his man one-on-one, doesn't pass the ball and all his teammates can do is just stand around and wait for Melo to either make his shot or miss. It's the exact opposite of the passing, moving without the ball offense past Knick coach Mike D'Antoni tried to use in NY (and probably why the Knicks can't seem to get the Phil Jackson triangle offense working with Melo in the lineup).