Thank you bsms for explaining the term!
The worst horse ---a pony--- I worked with would take a beating, because he wanted to fight. From the first reprimand I knew if there was ever a fight, I would lose. He used any excuse to blow up, starting with touching him with a brush!
I went to a book by Lucy Rees, to try to understand him. I ended up experimenting with being what I called a "benevolent fence post." Just did not respond AT ALL to his attacks. (I noticed he never attacked fence posts). I spent most of my time staying out of his way, as you can imagine. Bringing him in meant wrapping his mouth with the rope as I led; I cross-tied him; used ropes constantly. He was okay with all of this, interested even. I understand a professional trainer would never have the time to use this method!
If I thought an aggressive approach were needed, I'd call my trainer!