I have to disagree with Scott. Uprising almost always suggests more than one person is involved in the act of rising up against someone or some group (thus it would be organized), whereas it makes just as much sense to use rebellion in "the teenager's parents were met with rebellion when they asked him to abstain from alcohol until he reached the legal drinking age" as "the tea party committee demonstrated their rebellion against the obama administration at the rally" (the first is an example of something that is not organized). And it's true that, as mentioned in the definition, uprising also typically relates to political struggle. So, in my opinion, uprising suggests a specific kind of rebellion done in a group, but rebellion itself simply a broader term for an act of defiance. One thing to note is that neither word specifically connotes physical violence (as you can demonstrate both in a non-violent way), but it is something that is implied through context.