A memory of something that never existed in the first place, also known as a "false memory", but fancier.
J: "Remember that one time I ate lead paint and then crawled on the ceiling?Hahah, that was funny, right?"
G: "N- ... No, that ... That never happened. You feeling alright?"
J: "Oh. I guess I had another memoric hallucination. It's fine. I'm fine. It's fine."