Inferential role semantics is an approach to the theory of meaning associated closely with accounts of proof-theoretic semantics in the semantics of logic into work as the foundational formalism of logic. Gerhard Gentzen, Dag Prawitz and Michael Dummett are generally seen as the founders of this approach; it is heavily influenced by Ludwig Wittgenstein's later philosophy, especially his aphorism "meaning is use".
Jerry Fodor coined the term "inferential role semantics" in order to attack it as a holistic (ie. essentially non-compositional) approach to the theory of meaning.
It can be seen as opposed to truth-conditional semantics, just as proof-theoretic semantics is usually seen as opposed to Tarski's semantic theory of truth.