4D Studio: What is 4D?

I had some trouble figuring out what 4d is compared to what we are doing in this class. It seems that some people use the term 4D to describe their work as superior. I believe that for our purposes the fourth dimension can be anything above 3D such as Time, Movement, or Sound. This can include kinetic sculpture, animation and who know what else, it’s art and it’s subjective to the creator and the viewer