The definition of transdisciplinary, as given by the Institute for the Future is "the ability to understand concepts across multiple disciplines". Since 2005 there has been a lot more academic research conducted on transdisciplinary learning and education, yet it is still quite a new approach.
I wrote a blog post about future work skills and the future of education about 3 years ago, based on the work of the Institute for the Future. In this publication, based on what will be needed in the 2020 workplace, there are 6 drivers that are reshaping work, such as a globally connected world and the rise of smart machines, and there are 10 skills that are identified that workers will need. As you can see in the graphic below, transdisciplinarity is one of these. Many of today's problems such as global warming, over-population and so on, are too complex to be solved by the knowledge of any one discipline, and this has implications for the skills that workers will need in multidisciplinary teams to solve problems. This is why transdisciplinary approach to learning is so important: it is giving our students the skills and dispositions they will need for their futures.