Depending on the context, Systems Architecture can in fact refer to:
the architecture of a system, i.e. a model to describe/analyze a system
architecting a system, i.e. a method to build the architecture of a system
a body of knowledge* for "architecting" systems while meeting business needs, i.e. a discipline to master systems design.
* consisting in: concepts, principles, frameworks, tools, methods, heuristics, practices

Thanks,

http://www.systemarchitects.ca/