Green’s Dictionary of Slang

useless, nonsensical, absurd.

1942		P. Larkin letter 26 June in Thwaite Sel. Letters (1992) 34: You pick up any two bob pocket magazine [...] & you’ll find bullshitty poems or tossy ‘Short Stories’ all by our Sidney.
2022		A. Kirzman Giuliani 272: ‘He gave an answer that was [...] vague and bullshitty’.