bullshit = 廢話 bullshit is an impolite expression. So, bullshit in slang is interpreted as 放屁 is also appropriate

意思是废话

You re right,It is better for girl who never say it.

哈哈！你放屁啦！哈哈哈 bullshit=胡说 胡说=放屁 so bullshit=放屁 哈哈哈 =D