Harry G. Frankfurt, a real philosopher, provides the most useful definition of "bullshit" that I know of: the object of bullshit is persuasion, regardless of truth or falsehood.
If you're interested, Princeton University Press as a couple of five minute videos in which Professor Frankfurt expounds on his theory of bullshit.
Lindsay Beyerstein also produced a 30-minute talk for the Center for Inquiry that touches on Frankfurts work and its application to current events in 2016.
It bears mentioning that it doesn't matter how sincere you or the person you're listening to is. Sincerity is also a sign of bullshit; sincerity is about persuading others that you believe your own bullshit.
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