Are armed rebellions considered to be social movements?
Although we generally are not talking about armed rebellions or revolts when we talk about social movements, there is nothing in the definition of a social movement that would prevent a violent rebellion from being called a social movement.
Social movements are generally defined as acts that are done outside the established institutions of politics by people who want to either promote or block social change. We tend to think of things like the Civil Rights Movement when we think about social movements because it was a movement that went outside political institutions (by doing protests) to promote social change (equal rights for African Americans). However, we could clearly look at something like the American Revolution as a social movement. This was a movement that went outside normal politics (by things like the Boston Tea Party and eventually by war) to promote a social change (a change to self-government).
So, it is possible to categorize armed rebellions as social movements even though we do not usually think of them in that way.