Oooh! (raising hand) I know this one.....
Bone staight = hair with absolutely no curl or a very slight (and I do mean slight) wave when wet.
Over processed = hair? what hair? Oh, that hair in the comb, the brush, on the floor, in the sink. Every where but where it's supposed to be: on your head.
Over processed hair is very, very weak, brittle and breaks easily. Depending on your hair type, regimen, styling methods, etc. being bone straight is just a step away from being over processed.
It's a very fine line. How do I know?
Because that was me this summer. I was using a lye relaxer so moisture loss wasn't really an issue for me. I was doing fine until my heat fiasco. You have very little wiggle room if you relax bone straight. I can't do it any more....texlaxed is better for me.
HTH