1. Past tense of bullshit is Bullshitted, or sometimes bullshit, or very rarely bullshat.

2. Bullshit (third-person singular simple present Bullshits, present participle bullshitting, simple past and past participle bullshitted or bullshit or (rare) bullshat) (transitive, intransitive, vulgar, slang) To tell lies, exaggerate; to mislead; to deceive.