There is one way it could be made meaningful, but that way will never be accepted by those who use the word. It would mean all those groups and persons who actively engaged in or supported the Moscow Purge Trials. That's what the word is always associated with, but users of it would not want to be precise, because then it would use its scare-value.
Some people also call themselves Stalinist merely to indicate that they are real serious reds.
Carrol