Blocking or denial is a term used in theatrical improvisation (or improv) and theatre sports to designate an actor who does not accept the dramatic world set up by other actors and declines 'offers' made by an actor to come into that dramatic imaginary world.

Most often blocking is due to inexperience or misunderstanding on the part of an actor. It is viewed as the worst possible behavior for an actor in improvisation, and thus rarely seen when improvisation is performed with trained improvisers. Improvisation | Stage terminology