Slipping is NOT head movement?

[Chris Nagel]

I still don't understand the difference. I thought they were the same. Slipping is avoiding a punch, and head movement is what you do between punches, correct? Both I thought were considered "head movement".

The key difference is that "slipping" is when you are seizing an opportunity and deliberately avoiding a punch through head movement rather than otherwise incidentally. This requires the precise timing of a punch and then avoiding it. I suppose that you could look at it as a very important subcategory of head movement with a more specific purpose. For instance, actively slipping the jab and then countering.