There are a lot of B-School competitions doing the rounds on sustainabilty, and it set my curious alarm ringing. A bit of googling and asking around and some really good information materialized.
There are many definitions to sustainability and it can give rise to hotly contested debates. But one of the closest and very simple ones comes from Professor Rebecca Henderson, Business strategy expert and MIT Sloan professor :
Ways for economic activities to not actively degrade the future capacity of natural systems
Need to reduce carbon, water use, and waste and to build sustainable societies and personal lives
http://sloanreview.mit.edu/beyond-green/hundreds-of-gallons-of-water-in-every-shirt
The above link sheds more light on sustainability and the fact that your shirt might just have consumed hundreds of gallons of water in its making!
Very informative, I must say!