In academic settings, it’s also plagiarism to copy your own previous work. Given that, I’m not sure academia gets to take the high ground on what constitutes misconduct or not wrt to plagiarism, at least in the edge cases.
It's often denoted plagiarism or self plagiarism as a short cut. While it's probably better denoted duplicate publication (or similar) it still constitutes a similar academic misconduct, because you're pretending something is novel without it being novel
As a side note quite often it can actually be literal plagiarism as well, many journals require you to assign copyright, so using that work without attribution is plagiarism.
