Two, or more, actors on stage will start a scene where they move their mouthes as if speaking, but the dialogue is supplied by another performer.
Low Budget Voice Over is a dubbing handle where one performer has to supply the dialogue for all the performers on stage. Two, or more, actors on stage will start a scene. When they move their mouths the dialogue will be supplied by the designated performer.
Three performers on stage supply the dialogue for each other by dubbing vacant blath.ering mouths