Quick Definition: Agnostic about reality and what can be known
From Rational Wiki:
Pyrrhonism is an ancient Greek philosophy of extreme skepticism. Pyrrhonists hold no dogmatic beliefs about reality, neither affirming that reality can be known or that it cannot: rather the Pyrrhonist says that investigation has so far not reached a conclusion and so judgement is suspended. Pyrrhonism is named after the Greek philosopher Pyrrho, who was one of the first advocates of extreme skepticism.