I can't help but think of George McFly when I hear this word. However, it has never once been used in reference to George McFly. Rather, it has always, without fail, been used to describe the writing style utilized in scholarly publications.
Journal articles are dense. They are dense in that the meaning per word ratio is intentionally very high. The goal is to pack as much meaning into as few words as possible. For example, this paragraph is not dense in that I am making the point a couple of times in slightly different ways. There is no room for this kind of writing in scholarly journals. Repeating yourself is a waste of space and paper. Yes, going over something more than once is unacceptable in scholarly writing.
As you can see, I am going to have a hard time being dense - in my writing that is.
Furthermore, there is usually a certain hint of "I'm freakin' smart because I understand this article" going on when someone talks about how dense the article is. And thusfar, everytime I have sensed this assertion of intelligence, that person was actually super smart.
Well, I am learning to write scholarly. I might even annoy you with something posted on this blog at some point in the future. Hopefully, I can be your density.