Realizing this might be almighty threadomancy, here's my 2 cents: In the general sense, a conspiracy is a gathering of 2 or more individuals covertly working together in order to realize their illegal goals. I'm not saying all illegal goals are illegit goals: many resistance-fighters have to work covertly in order to avoid capture. However, in the specific sense, 'conspiracy' to me means the working together of people within an institution or government, working together in such a way as to avoid detaction of their illegal (as well as illegit) goals, executing actions which by their nature alone are only beneficial to this small group. In other words, a conspiracy is a small group breaking rules of law as well as making laws in order to further their own plans from which they themselves will benefit, and the majority of the world will not. Should I find more nuance, I will adjust my statement.