1/ Collusion has become a short hand term that is widely used for the entire range of conduct Trump & people in his orbit have engaged in, that makes us suspicious about his relationship with Russia.
2/ Today, in the face of mounting evidence that Trump may have had advance notice of the Trump Tower meeting with Russians, Rudy Giuliani engaged in his most recent goal post-moving exercise, maintaining that even if there was collusion, it's not a crime.
3/ Technically that's true, in the sense there is no crime titled "Collusion." There is, however, the crime of conspiracy–an agreement between 2 or more people to defraud the US. One of the coconspirators must take a step towards the crime, called committing an "overt act."
4/ So, Rudy says Collusion, Mueller says conspiracy. No court is going to call the whole thing off on that basis.
5/ To close the loop, there is a law that prohibits "collusion." 18 USC 201, the fed'l bribery statute, makes it a crime for a public official to seek or accept a thing of value in return for colluding in a fraud on the US. So, it's entirely possible collusion isn't dead yet.
