To use "expedite" means the controller has made a mistake...or maybe the pilot has made an error
That is the same as saying that a TCAS RA is as a result of an ATC error!!
Expedite is a fairly clear English term which the dictionary defines as "to accomplish quickly" Therefore if I give an instruction to climb FL110, expedite through FL80 it doesn't mean that I have 'made a mistake' it simply means that I have traffic at or descending to/through FL70 and I just want to get you through it a little quicker. But expedite is not a form of separation I hear you tusk - correct, which is why I will only do it with the a/c on headings (probably converging) and I can then 'tweak' one if the expedite isn't expeditious enough. Without this term, there would be a hell of a lot of a/c stuck down for longer within the TMA