What term refers to a single curtain that moves across a stage to hide it from view?

The correct term for a single curtain that moves across a stage to hide it from view is a "wipe." In theatrical contexts, a "wipe" refers to a type of curtain movement, often used in transitions between scenes, that effectively conceals the stage area from the audience. This technique creates a smooth visual transition and can enhance the flow of the performance by allowing for quick changes in scenery without revealing backstage activity.

The other choices do not relate specifically to the function of concealing a stage. A wagon stage refers to a type of stage that can be moved on and off the playing area. A thunder run typically describes a specific sound effect or sequence intended to create dramatic impact. Costume designing pertains to the creation and planning of costumes for characters, which is unrelated to the physical concealment of the stage. Thus, "wipe" accurately describes the operation of a single curtain moving across the stage.