I've noticed that even some people who have a fairly solid grasp of Korzybski's work continue to say and write 'Null-A' when referring to the 'A with a bar above it' which Korzybski used as an abbreviation for 'Non-Aristotelian'. However, understanding the confusion that so many people have had about Korzybski's take on Aristotle and aristotelian logic, it seems to me a mistake to use the term 'Null-A' when seriously referring to Korzybski's work.
Neither Korzybski, nor any of his close students who taught for years at the Institute of General Semantics like Charlotte Read and Allen Walker Read, nor his students' students like Robert Pula, ever used the term 'Null-A' to refer to what Korzybski purposely called 'Non-Aristotelian'. Indeed, Pula, the lead lecturer at Institute seminars across four decades, specifically advised eschewing the term 'Null-A' except when talking about the titles of A.E. Van Vogt's science fiction works. As far as I know, the term 'Null-A' seems to have first been used by A.E. Van Vogt in his 1945 science fiction stories and the 1948 hardback novel published from those stories. Van Vogt specifically used the term 'null-A' to refer to Korzybski's symbolic abbreviation for 'non-aristotelian'. The original title of the book simply used the symbol, The World of [an A with a bar above it]. The book's title was changed to 'The World of Null-A' in later editions. In light of the science fiction origin of the term that Korzybski never used, why use it when seriously discussing his work?
Korzybski stated in numerous places that he did not intend non-aristotelian as 'anti'-aristotelian. Contrariwise, 'null' tends to get interpreted as negation, absence, elimination, anti-, etc. Since the socio-cultural-historical 'baggage' of a term can influence those who use it and hear it (what I have called elsewhere the 'neuro-linguistic undertow' of a term), it seems to just increase the probablity of misunderstanding to use 'Null-A' when seriously writing about or teaching Korzybski's system.
Needless to say—but better to say it—Korzybski had no interest at all in 'nullifying' Aristotle's logic. For him, aristotelian logic remained useful where it applies. He didn't want to do away with it. He simply didn't think that it, or rather the underlying structural assumptions about the world that tend to accompany it, should be used as a general orientation for life. General orientation, cultural and personal. That—not 'logic'—mainly concerned him.