GTO (game theory optimal)
Also: game theory optimal, unexploitable play
A strategy that cannot be exploited by any opponent because every decision is balanced between value and bluffs at the frequencies the maths demands. Solvers compute GTO strategies; humans use them as a baseline and deviate to exploit mistakes.
GTO does not mean 'always winning'. It means your opponent cannot gain by changing their strategy against you, whatever they do. Against a perfect opponent that is the best you can achieve; against a weak one a purely GTO player leaves money on the table because they never punish specific leaks. Modern high-stakes players study solver output to learn the shape of balanced strategies — bet sizes, frequencies, which hands bluff — and then apply exploitative adjustments when they spot patterns. The opposite pole is exploitative play, where you deliberately play unbalanced because the opponent will not punish it.