"BIM is the virtual representation of the physical and functional characteristics of a facility from inception onward. As such, it serves as a shared information repository for collaboration throughout a facility's lifecycle." - Patrick Suermann, PE. NBIMS Testing Team Leader
"The process of modeling and communicating the structure of a building in detail to benefit the entire building lifecycle. BIM facilitates the exchange and use of building information in digital format. The acronym BIM is also used for the terms 'building information model' and 'building information management'." Source: http://www.tekla.com/international/solutions/building-construction/Pages/basic-concepts.aspx#bim
I think any discussion of BIM ("little bim", the desktop technology) is incomplete without a corresponding discussion of IPD (integrated Project Delivery, aka "BIG BIM".) It is reasonable to argue that "little bim" is really just better CAD, while IPD is the change in the construction industry that will deliver the greater benefits. Because IPD requires a high degree of collaboration, communication, and pro-active project planning in a non-litigative legal setting, it may be that IPD is what really delivers the goods, even more than the desktop technology.