Which definition best describes a mural in art?

A mural is best described as a large-scale artwork that is applied directly to a wall. This definition captures the essence of murals as they are typically expansive and create a direct impact on the viewer within the environment where they are situated. Murals can be painted or produced using other materials and are often intended to be part of the architecture or the surrounding space. They are usually meant to be seen in situ, blending with the architecture while transforming the common wall into an artistic expression.

The other choices do not accurately capture the definition of a mural. A decorative panel in a private residence refers to smaller, often framed artwork that is not necessarily integrated into the structure itself, limiting the scale and context typically associated with murals. A miniature piece meant for display suggests a limited size and doesn't convey the large and encompassing nature of a mural. Lastly, a temporary exhibition space implies a location rather than a particular type of art form, which does not align with the established understanding of what constitutes a mural in the art world.