One note: A cut direct is a severe cut. As such, it is thrown around EHell more often than it should be. Some posters don't realize just how severe it actually is intended to be. One of the other cuts (indirect, sublime or infernal) would be more suitable for most of the situations encountered here.
As commented by Agnes H. Morton (1892), "The “cut direct” is the rudest possible way of dropping an acquaintance; and is allowable only in the case of some flagrant offender who deserves public and merciless rebuke. Ordinarily, the result sought— of ending an undesired acquaintance—is attained by a persistently cold courtesy, supplemented by as much avoidance as possible; drifting apart, not sinking each other’s craft without warning."
Also, "One thing to understand about the cut direct is that it is a public shaming. Not answering your door, replying to a letter, or answering the phone—these are not examples of a cut direct. A cut direct is looking at someone straight on and pretty much pretending you don’t see them*. You are informing those present that they are unworthy of your acknowledgment. Pretty harsh."
* A post above is an example of how this cut is not understood completely. It is not avoiding looking at them. It is, rather, looking at them straight on and pretending you don't see them.
I agree with this. You can cut someone out of your life without doing a cut direct.
Imagine this scenario. Uncle Bob has done something which caused you to want to completely cut him out of your life which you have done. Unfortunately this means you no longer have a relationship
with Aunt Sue either. You encounter them at a funeral.
Bob: Hello, Hmmmm
Aunt Sue: Hmmm, I've missed seeing you, how is your DH?
You: Aunt Sue, it's nice to see you, sorry it is under these circumstances. DH is doing well
Bob: That's good. You need to come visit.
You: Aunt Sue, Bob, please excuse me. I need to speak to Aunt Agatha.
With a cut direct, you would completely look past the fact that Bob was standing next to Aunt Sue. You would not acknowledge him if he spoke to you. With a cut direct, it is very uncomfortable for all other parties witnessing the cut, and in this case your Aunt Sue. Which is why a cut direct is so severe.