Has "impenetrable" defenses

Finally, Starkiller saw an opportunity. They were exchanging rapid blows along the edge of the buckled platform, blades swinging so fast they were visible only as blurs. Vader’s defenses were impenetrable; his lightsaber seemed to arrive a split second before Starkiller’s, every time. He may have defeated Vader before, but Vader had learned from that mistake. He knew the measure of his former apprentice now.

The Force Unleashed 2, Chapter 23, Page 358