A "bullshit" solo in musician parlance is a solo that doesn't stay within the music's context. It is usually characterized by overplaying and being self-indulgent with too many notes, too fast, inappropriate effects, or trying too hard to be "hip" while not "saying" anything. Often, this is done to hide the fact that the player doesn't have a good command of the tune's harmonic changes and simply plays a lot of shit that doesn't fit the harmony; or, at best, fits the harmony but is not fully developed as a spontaneous composition. A great solo always keeps a connection to the melody of the tune and simply builds on it. I know he has many fans, but for me a great example of a chronic bullshitter is David Murray:
https://m.youtube.com/watch?v=KrXIQ0_ogK0
https://m.youtube.com/watch?v=KrXIQ0_ogK0