There is already a question about this, Log out of all Stack Exchange sites with linked account simultaneously, but unfortunately it hasn't been updated, like also this one, Can we have a "log out on this computer only" button?.
Currently the log-out page says:
Clicking Log Out will clear our cookies and log you out of Stack Overflow on all devices.
If you're on a shared computer, remember to log out of your OpenID provider (Facebook, Google, Stack Exchange, etc.) as well.
But still if I log out of meta, and the open stackoverflox, I am logged in again. Do I have to log out from my email (that I use for OpenID), and then login again to it for, ehm, checking my email?