What is Buffer State?

it is a state when the acidity or bascity of solution doesn't changes with the addition of small amount of acid or base.

A buffer state is a region falling between two rival or big states. Tibet was considered buffer state between India and China before merger.

I think there is one more meaning of buffer state. It means the area where no one can rule. It is considered in army. At the border, where no one can rule on that area.
Correct me,if i am wrong.