I haven't read Harry Frankfurt's 1986 philosophical treatise On Bullshit. But here's a summary I like from its Wikipedia page:
In the essay, Frankfurt defines a theory of bullshit, defining the concept and analyzing its applications. In particular, Frankfurt distinguishes bullshitting from lying: while the liar deliberately makes false claims, the bullshitter is simply uninterested in the truth. Bullshitters aim primarily to impress and persuade their audiences. While liars need to know the truth to better conceal it, bullshitters, interested solely in advancing their own agendas, have no use for the truth. Thus, Frankfurt claims, "...bullshit is a greater enemy of the truth than lies are."This does seem to be the defining characteristic of bullshitting - the lack of regard for truth. And it does seem to be more dangerous than lying, for the same reason that a machine learning classifier with 50% accuracy is far less useful than one with 10% accuracy.
However, bullshit can describe many things beyond statements with a truth value. For example, we talk about bullshit jobs. What exactly is a bullshit job? Is a bullshit job just one that requires you to generate bullshit statements? I think there's more to it than that. There's a whole book on bullshit jobs, and it provides us with some useful examples: cheese artisan (sculptor of supermarket cheese), feng shui consultant, economist, aromatherapist, life coach, and so on, though some unfortunately stray from bullshit territory into mere unpleasantness (roadkill collector) or overt detriment to society (patent troll).
What do these jobs have in common with Harry Frankfurt's definition, the lack of regard for truth? Certainly some may require explicit truth-disregarding, but I think a more fundamental similarity is the idea of a broken link to what really matters. For bullshit statements, the link between a statement and its truth value has been severed. Again, this is different from false statements, in which the link is present but set to "reverse". And bullshit jobs, then, are jobs which provide no direct benefit to society, and for which the indirect benefit requires a link which has been severed or never really existed at all.
What "really matters"? I'd say something that makes a person happy, though you can use whatever rule you want, as long as it isn't "nothing". Or, I suppose, if you say nothing matters, then you should conclude that everything is bullshit, which might be a defensible position. And keep in mind that there's lots of non-bullshit that is pretty far removed from mattering, like designing uniforms for train conductors, but that remain non-bullshit as long as the intermediate links hold up. In many cases it may be difficult to test all of these intermediate links, and in fact the increasing specialization in modern society may be the cause of the proliferation of bullshit. I'd guess that hunter-gatherer societies are able to get away with considerably less bullshit, because the links to usefulness of any activity are easily testable by anyone.
Looking it at this way, a large fraction of what we do all day is bullshit. From personal experience, most of what happens in academia is bullshit. 99% of research papers, including (especially?) the ones by me, are bullshit, even if every single statement in them is intentionally true. The business world, notorious for its bullshit, actually seems a little bit better. From what I can tell, tech startups seem to have relatively low levels of bullshit. At least, the good ones do - some have made my life noticeably better. And things like baking and selling bread are about as far from bullshit as you can get.
