I think I've answered my own question about the meaning of 'populism', or at least the right-wing kind: the fake anti-elitism of people who are, economically at least, even more elite than the bulk of the 'elite' they attack, but give the appearance of being outside of the elite because they're "not encumbered by [the] political correctness" that characterized the speech of establishment politicians (i.e. are racist/sexist as fuck), and which appeals to the (justified) economic grievances of both working- and middle-class voters (white ones, at least) who have abandoned/feel abandoned by the left, as well as antagonizing deep-seated prejudices.
A big part of it is the (usually totally false) impression of having 'made it from nothing', or at least from very little, e.g. Trump's claims about 'being the most successful living American' vs. the reality of his having inherited a large share of his father's property empire.