Don’t want to split hairs, but since the question was apparently about “bumping topics” more generally, it’s worth mentioning that the term refers to bringing topics back to the top of latest topics regardless of whether this is done by the system or a human.
tl;dr bumping = resurfacing older topics by posting a new reply, auto-bumping = when this is done by a machine (and, I believe, a rather unique feature of discourse).