In a nutshell. Dropping a controversial or vitriolic opinion or one that requires substantial explanation and sourcing, and just bailing on the thread without reading any challenges to your train of thought.
Or just dropping in to say "this thread/topic sucks" which adds nothing to the discussion. Or derailing a discussion because the original post makes you uncomfortable. Thread shitting/drive by posting is the equivalent of "dropping the mic" before anyone even hears your opponent.
When someone leaves a short comment designed to dismiss a thread, a poster, a comment, or an opposing position; often with phrasing implicitly designed to create the illusion their own position is both unquestionably true and respentative of popular opinion; without providing any argument or sources of their own to be attacked or questioned by those they dismiss; and by immidiately leaving the topic to deny their opponents any subsequent posts to find any further statements that could be critiqued while also creating the impression that those they dismiss are so unworthy that they do not deserve responses.
And then there's the low-effort drive-by hit posts that attack the thread, poster, comment, or general position without sources because they don't have any sources; have no argument because they can't make a good one; and they leave because their can't or are afraid to defend their comment. They just wanted to leave something to steer the greater audience towards their side and then quickly move one.
A combination of these, plus also:
When people come into a topic, and just post a response either just to the OP, or just to the topic title, when that post has been made plenty of times in the topic already, but for some reason they think it's new/clever/worth posting.
If a topic has 300 posts in it, and you're posting a random comment to something from the OP, there's a good chance that thing has been said and discussed already.
And, since I checked and don't see this part of the OP replied to specifically:
Like, it seems to mean someone who just reads the OP and then makes one post and leaves, but I don't really see how that's any different from typical forum behavior. I mean, this site is set up to respond to have topics that you respond to. On other forums the majority of posts that I've seen would probably be categorized as "drive bys".
If every other forum jumped off a bridge, would you jump too?
Just because something is common/accepted elsewhere (or even here) doesn't mean it's good practice/conducive to good conversation.
