Unblocked, ignored.
And not like some kind of Lawrence Taylor - Im going to run down the RB on a sweep away from me thing.....just a normal play where that successful defensive play had no obstacle.
Ahh. Interestingly, this would actually be a semi-good use for PFF. (I was looking for a video example, if you had one)
The problem with this thing you mention is that being unblocked is often not being ignored. And it can be for many sorts of reasons. Sometimes its because you're fast. Sometimes a line communication. Sometimes an unblocked backside DE gets a TFL because the front side set the edge well. Sometimes you scheme up a really nasty blitz. And sometimes it's just a pain to tell that.
I was at a game a few years back. One of the first plays, the tackle in front of a stud DE blocks down, he races at the handoff unmolested, TFL. A guy near me curses about the tackle, and I'm sure a lot of folks would see it and say "that fella was unblocked and ignored." Only the play was counter, and you had a guard coming across to get him. Now, that guard was not fast and the DE was, and thus, races in untouched. But it wasn't a freebee.
Like, no plays are designed simply not to account for someone. They account for them in different ways. Sometimes that way doesn't work out. And the meaning from those stats would just not be worth the time. You'd actually be better off tracking the inverse, something like defeated blocks or tackles made when somewhat blocked.