Big Book of Bullshit Share definition Flag A term to use when someone is clearly full of bullshit. Person 1 : "The sky is green!" Person 2: "Where'd you get that from, the big book of bullshit?" Big Book of Bullshit by jag928 June 7, 2011 0 0 Get merch Get the Big Book of Bullshit mug. Buy Now — $32.95 See more merch