Here is the meaning from wikipedia..
"In software engineering jargon, a greenfield is a project which lacks any constraints imposed by prior work. The image is that of construction on greenfield land, where there is no need to remodel or demolish an existing structure. Such projects are often coveted by software engineers for this reason, but in practice, they can be quite rare."
I think it means a fresh implementation of SAP(and BW) for the client(not upgrade etc) without dependencies on phasing out any legacy systems being used (earlier) by the client.
Such projects are rare.
Message was edited by: Vishvesh
A "Greenfield" or "Vanilla" implementation is the traditional way of implementing a SAP system. The team which consists of both consultants and key users starts from best practices and designs the final ERP-solution taking into account the teams joint experience. After the design-phase the team starts configuring the solution and goes to a formal process of training, workshops and configuration iterations until the final solution is accepted by the key users and process owners (the customers management). In the next phase, the end-users are trained, all data is uploaded and the system "goes live". After this a process of continuous improvement starts.