Take your pick from this link:
http://blogs.msdn.com/b/nickmalik/archive/2012/09/11/many-flawed-definitions-of-business-architecture.aspx
Although the following looks rather good:
Doug McDavid from November 2007 in "The Business Architect - An Emerging Role" defines Business Architecture as:
"Business Architecture is the art and science of delivering coherent, dynamic and complete business designs to drive successful business transformation. It is an architectural view of business that organizes:
- A rigorous description of current and future states of the business as well as the intent and realization of business operations and initiatives;
- The definition of initiatives to measure and improve business performance and realize strategic business intent; and
- The context for IT transition planning and roadmap development."
