Ok: "In political science, a revolution (Latin: revolutio, 'a turn around') is a rapid, fundamental transformation of a society's class, state, ethnic, or religious structures." - Wikipedia. The page actually spends quite a lot of time expanding on that definition, including several notes that it is often considered necessary to have an extrasystemic component, that is, that a reform from entirely within the system would not count as a revolution. My point was more that revolution is a type of reform, rather than that reform is a type of revolution. You can fix a system by replacing it. You can also fix it in place. There is no fundamental obstacle that appears in the latter case.

Interesting link. Will read.