For once, there appears to be a measure of agreement on the definition side when it comes to Web Services. Unlike many other computing models, the whole field is so new and fresh as to allow a consensus of opinion to hold sway rather than have multiple definitions that have been corrupted by vendor-specific marketing hype used to promote a sub-set of a larger picture.
Even so, a definition can take many forms depending upon the viewpoint, and Web Services is no different in this respect. To cover the different viewpoints, Web Services can be given three definitions with the following emphases:
Web Services is a standards-based initiative that aims to bring together existing protocols and standards, and tie them together in a way that allows the delivery of fine-grained components using the Internet as the backbone method of delivery.