Revolution. There are four dictionary definitions of the word. (Three entries, but four seperate definitons shared between them.) Two refer to physical events, two to metaphorical or political ones. My meaning is related to the two metaphorical definitions, but it falls somewhere in between them. Neither really covers exactly what I mean.
It makes mention of "overthrow of one government and its replacement by another." This catches part of my meaning, because my particular definition of revolution is concerned with governments. However, it is not concerned exclusively with governments. Further, the idea of government -- for simplicity, defined as "a group of people who make decisions for a larger group of people" -- is simplistic and outdated. I'm interested in the overthrow of governments, but the replacement of said governments with other governments is beside the point.
"A sudden or momentous change in a situation" also encompasses part of my definition, but not all of it. There's nothing in my definition of revolution of how long it takes. It could take a day, a year, an entire generation. Longer. It's still a revolution, if it completes the basic requirement.
A revolution has happened when things started one way and ended in a completely different way.
It's broad, somewhat clumsy, and lacks a certain linguistic panache. But it works, because it catches both the military and civilian, governmental and societal, and it ignores things were a new group of people took over but nothing really changed. So when I talk about revolution, that's what I mean.