I found the following statement of interest because it is a succinct way of explaining what is meant by 'transdisciplinary' without using the phrase "interpenetration of disciplinary epistemologies" (which just makes eyes glaze over):
"Boundaries for transdisciplinary courses are the boundaries of the problem being addressed, not the artificial boundaries of disciplines".
This was made in the context of a discussion of a transdisciplinary model for research and education as applied to engineering on the website of TheATLAS - which (according to its own blurb) is a non-profit organisation providing services to universities around the world.
I also noticed that the new MFA Design curriculum (starting 2007) at the California College of the Arts is using the term 'transdisciplinary':
"As our world and cultures undergo radical transformations, so the role of design is growing and changing. The professional design world increasingly values broad, transdisciplinary design knowledge complemented by virtuosity in specialized fields ... Design continues to grow beyond the traditional notions of designing objects and messages and toward designing change—through transmedia systems and cultural interventions. As the boundaries between traditional disciplines blur, new forms and methods are emerging. Tomorrow's designers must comprehend a much broader realm of practice, and must likewise be ready to embrace greater opportunity and leadership in shaping the future of culture in fundamental ways."