Wow. In some ways, that's the worst possible answer. In my view, software architecture is what every developer contributes to, which means we have to be thoughtful about how we collaborate on it.
Every time I see a shop with designated Software Architects who hog the architecture work, it's a fucking mess. Because then Software Architects don't get rewarded in their careers for making software. They get rewarded for writing white papers and coming up with "brilliant" architectures and impressing executives who know less than them about technology. Which is mostly inversely correlated with actually making it easier for developers to get real work done.
At OOPLSA 98, Booch convened the first society of software architects (or some such).
Having read all his writing (ditto Yourdon, Brooks, Rumblaugh, etc), I was super excited.
During the Q&A I finally got to ask “What is software architecture?”
Booch replied “Software architecture is what software architects do.”
Bubble popped.
I gave up seeking the council of the priesthood and blazed my own path.