I think the bullet points of how to describe defensiveness are quite useful. For me it moved things away from "I know it when I see it", and more toward defining the behavior itself. This is useful because if you were to get to the point of having to give someone feedback about how they get defensive, it is most useful if you can point out specific behaviors they need to improve, and it's a lot easier to do that if you've defined what you're looking for in the first place.
Another version of this I've seen is deflecting -- where the person receiving feedback always has another person to blame for why things went wrong. In an isolated instance, this isn't necessarily a problem: maybe they're right! But if this is their response every time a problem is raised, it becomes a patter of avoiding addressing the feedback you're giving them.
The point about not giving enough feedback in general hits home for me. I think I need to get better at giving positive feedback more often -- which also improves your ability to give negative feedback when necessary.