False seki
A false seki is a position that looks like a seki but is not, because one player's stones are actually dead. A false seki may be a temporary seki that has collapsed, or it may be a position that arose in killing the dead stones.
Examples:
Discussion
Bass: To me these three final diagrams do not seem like examples of false seki. They are plainly dead (we'll talk about the bent four later ;-) ) and I do not think there is any need for a term that means "dead, but somebody once misread it as seki". However, the first diagram displays a "proper" false seki, where there are groups that are locally in a seki, which will however collapse because some of the surrounding stones will get killed. In my opinion, this is a much more useful meaning for the term.