The dictionary definition of 反动 means reactionary, and in the political sense it can also mean someone who is very conservative, as opposed to progressive.
However, it seems that this word is being used in a far broader sense, and with strongly negative connotations. For example, take this passage:
近代中国历届反动政府对内政策的出发点都是维护自身统治,推行专制独裁,镇压人民反抗,扼杀进步力量。
It seems that apart from the last of those four points, all could be used to describe any government, reactionary or not.
Or this passage:
指反动统治者自己可以胡作非为,老百姓却连正当活动也要受到限制。
Which describes unequal law instead of reactionary.
So what meanings does 反动 really have? And (although this one seems obvious) is such usage limited to PRC?