My Latest Hair Mystery

So I know I had promised to explain more about the reason behind my curiosity about scab hair in my last post but there was so much to write, it was already too long by the time I remembered this. So here it is:
I guess I should start first by explaining my hair texture...or at least what I have discovered about it.

My hair is very tightly coiled at the temples and nape and more loosely coiled at the crown, top and center and close to the crown at the back and sides. Thats all I can tell.
I don't really subscribe to hair typing, I am not sure about what the types mean and really, I just find the typing prone to being inaccurate and limiting. There is no definitive line between  a 3c versus a 4a for instance, its perception and somewhat relative. So I just note the curls. Not any coils as far as I can see (s-shapes) but I can't be sure.
The middle of my head, the crown, puzzles me. It's somewhat wavy, definitely no curls and I have not noted coils or s-shapes. When I was a little girl, the little I remember about my hair was the the middle grew the fastest, and retained length the most, but now back to my natural state, it is the most unresponsive and puzzling part of my head.
I recently read a post on a random blog about scab hair and how it doesn't respond to products and suspected this of the hair in this part of my head. But I wouldn't say it doesn't respond to products, it just waves slightly in response, no definitively tight curl like my nape or looser but still definitive curl like the top of my head, it just seems like it doesn't know which way it wants to curl or what, if anything, it should do.
I felt the roots thinking I should feel more definitive curl pattern there if, say, during my transition phase (where I did blowdry and flat iron frequently) I damaged the new growth that would now be the ends on my current head of hair but the root feels the same. So I want to know: What is scab hair?
I am puzzled.....