TQBF

Etymology
From True (or totally) quantified Boolean formula.

Symbol

 * 1)  The decision problem of, given a Boolean function f on n variables, deciding whether the following formula is satisfiable:
 * $$\exists x_1 \forall x_2 \exists x_3 ... Q_n x_n f(x_1, x_2, x_3, ..., x_n)$$
 * Where $$Q_n$$ is $$\forall$$ if n is even and $$\exists$$ if n is odd.