I think you are getting bogged down in definitional issues that do not really help clarifying anything.
The constitution is written in English, anybody can read and interpret it and many people have done so. Unless you subscribe to the view that the constitution has no meaning whatsoever beyond what the court said about it, you have to recognize that some things can in principle be coherent with its contents and others cannot. It's convenient to have an adjective for that and I would contend that in English that word is “constitutional”, simply because it's the way in which English speakers use it.
Using the word “constitutional” based on such a personal interpretation of the constitution obviously does not imply that the person using it has the power of invalidating a given norm within the US legal system or that the US supreme court would necessarily subscribe to the same interpretation but why should the word “constitutional” solely be defined by that?
The analogy with criminal law discussed in the comments is a good one. If you go too far in the “the law is only the courts' decisions” direction, you have to conclude that a murder is not a murder until a court says that it is. But that would strike most people as absurd, everybody (including the courts themselves!) act as if there really are laws forbidding murder and not only individual decisions that judges pull out of their hats.
Similarly, the constitution is the basis for deciding what's constitutional or not. Equating “constitutional” with “validated by the constitutional court” is possibly still defensible for an observer but it is obviously useless for the court itself because it would be left with nothing to justify its decisions. Although judges sometimes do appear to take some freedom with the letter of the text, they certainly mostly pretend to be following the law (in this case “discovering” whether something is constitutional or not, as it were), not making it up as they go. They have to assume that the constitution really has a meaning and hence that things can be (un)constitutional even before they reveal their decision in a given case.
It also seems rather circular to request a US supreme court decision about this. Why should it have a monopoly on what the word means? Why would it even need to use it?